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Has Stonehenge drifted off its line? This post is the companion ...

2026-10-30T14:20:29Z

Has Stonehenge drifted off its line?

This post is the companion to the short film Has Stonehenge drifted off its line? Stonehenge was laid out on the solstice axis about 2500 BC. Three slow movements could have shifted that line since: the wobble of the Earth's axis, the easing of its tilt, and the drift of the ground itself. Only one of them has moved the solstice sunrise by a measurable amount. The numbers, methods and caveats follow.
The question
The main axis of Stonehenge runs from the midsummer sunrise in the north-east to the midwinter sunset in the south-west, at 49.95° true (49.81° on the National Grid; Thom et al. 1974). The sarsen structure is taken here as built about 2500 BC. The question is whether anything has since moved the line between the stones and the Sun.
Stonehenge in 2500 BC (red) and today, about 100 m to the north-east. The two axes are parallel. Plan from T. Daw's 3D model.
1. Precession: the stars change, the sunrise does not
The Earth's axis wobbles like a spinning top, tracing a cone about once in 25,800 years. The north pole of the sky moves with it. Thuban, in Draco, "passed within 0.1° of the pole in 2800 BC" (Rawlins & Pickering 2001); today the pole lies near Polaris. Using the long-term precession model of Vondrák, Capitaine & Wallace (2011) and Thuban's J2000 position (proper motion ignored), the closest approach comes out at 0.05° in 2791 BC, consistent with that figure.
Precession changes which stars stand behind the Sun at the solstice, and the calendar date of the solstice. It does not change where the solstice Sun rises. At a solstice the Sun's declination equals the obliquity, plus or minus, and the rising azimuth depends only on declination, latitude, the altitude of the horizon and refraction (Meeus 1998; Ruggles 1999).
The path of the north pole of the sky from 2800 BC to 2026 (gold), on its 25,800-year circle (dotted). Vondrák et al. 2011.
2. The tilt: the sunrise has moved about one degree
The obliquity, the tilt of the Earth's axis to its orbit, has fallen from 23.973° in 2500 BC to 23.436° today (Vondrák et al. 2011, through the ERFA library; Laskar 1986 gives 23.974° for 2500 BC). That is a change of 0.537°. Taking 2700 BC or 2300 BC instead gives 23.992° or 23.954°.
Where the Sun appears on the skyline also depends on how high the skyline is. The horizon was computed from the Environment Agency's 1 m LiDAR terrain model (5 m beyond 2 km), from the centre of the circle (51.1789° N, 1.8262° W) with the eye 1.5 m above the ground, allowing for the curvature of the Earth and terrestrial refraction. Stones and trees are ignored. To the north-east the skyline is a ridge about 2.7 km away, 0.57° high at the 2500 BC sunrise and 0.60° at today's. To the south-west it lies about 4.3 km away, at 0.46–0.49°.
With Bennett's (1982) formula for refraction and a solar semi-diameter of 0.267°:
Midsummer sunrise, first gleam: 49.33° in 2500 BC, 50.42° today, a shift of 1.09°. With the half disc showing, 49.79° to 50.86°; with the whole disc risen, 50.25° to 51.30°.
Midwinter sunset, last gleam: 230.02° in 2500 BC, 231.08° today, a shift of 1.06°.
The Sun is 0.53° across, so the sunrise has moved about two widths of the Sun. Moving the date of construction 200 years either way changes these azimuths by less than 0.05°. Refraction near the horizon varies with the weather by a few tenths of a degree; that moves both dates alike and leaves the shift unchanged.
The north-east skyline from the centre of Stonehenge, from Environment Agency LiDAR, with the first gleam of the midsummer Sun in 2500 BC and 2026. Vertical and horizontal scales equal.
3. The ground: Rujm el-Hiri
The third movement is the ground itself. Rujm el-Hiri is a large stone ring in the Golan Heights, about 150 m across, with a central cairn. Aveni & Mizrachi (1998) proposed that its layout held solstice and other sky alignments. Khabarova, Birkenfeld & Eppelbaum (2024) argued from geomagnetic evidence that the whole region has rotated, and that this undermines the observatory interpretation. Their figure (section 3):
"Assuming the average rotation velocity of 10 mm per year and the age of the studied prehistoric site as 4000 years, we will receive an arc rotation of about 40 m. The corresponding direct movement can be estimated as 30 m to its today's position."
The paper gives a distance. It gives no angle through which the site has turned.
The Sea of Galilee and Rujm el-Hiri. Lake outline: Natural Earth.
The rings of Rujm el-Hiri (schematic) and the paper's 30 m shift, drawn to the same scale.
A shift is not a turn
The Sun is so far away that its light arrives in parallel lines. Sliding a monument sideways, by 30 m or 30 km, leaves every bearing within it unchanged: a line that pointed at the solstice sunrise still does. To spoil a solar alignment, the ground has to turn, and by something like the width of the Sun, about 0.5°.
No rotation angle is published for Rujm el-Hiri. As an order of magnitude only: fast block rotations measured from palaeomagnetism run at 1–20° per million years, which over 4,500 years gives 0.005–0.09°. That is well short of a Sun-width. This bound is ours, not the paper's.
Diagram: a monument slid sideways still points at sunrise; turned, it does not. Movement and angles exaggerated.
Stonehenge on the Eurasian plate
Stonehenge sits on the Eurasian plate, which rotates slowly about a pole in North America. Evaluating the plate's rotation at the monument:
ITRF2014 plate motion model (Altamimi et al. 2017; Eurasia ω = −0.085, −0.531, 0.770 mas a year): 16.5 mm a year north and 16.5 mm a year east, so 23.4 mm a year on a bearing of 045°. Over the 4,525 years since 2500 BC that is 106 m: 75 m north and 75 m east.
NNR-MORVEL56 (Argus, Gordon & DeMets 2011; pole 48.85° N, 106.50° W, 0.223 ± 0.009° per million years): 21.7 mm a year on 043°, 98 m since 2500 BC.
These speeds are measured against the average motion of all the plates (the no-net-rotation frame), which is a convention. Relative to Africa or North America the figures differ; the rotation of the ground under Stonehenge, which is what matters for an alignment, does not depend on the frame chosen.
The Eurasian plate (shaded) and its boundaries, PB2002 (Bird 2003), with Stonehenge's motion. Inset: the monument's 106 m since 2500 BC, to scale.
Has Stonehenge turned?
The component of the plate's rotation about the local vertical at Stonehenge is 2.5 arcseconds anticlockwise since 2500 BC (ITRF2014; 1.8 arcseconds with NNR-MORVEL56), or 0.0007°. Moving 75 m north also raises the latitude by 0.00067°, which moves the solstice sunrise by 2.5 arcseconds, also anticlockwise. The monument and the sunrise have turned the same way by the same amount, so the alignment between them has changed by well under an arcsecond.
A larger term is polar motion: the slow drift of the spin axis relative to the whole crust. At today's secular rate of about 3.5–4 milliarcseconds a year, much of it from rebound after the last ice age and not necessarily constant over 4,500 years, it amounts to roughly 16–18 arcseconds of pole shift, of order 0.005°.
Taking everything together, the ground under Stonehenge has turned by less than a hundredth of a degree against the sky. The easing of the tilt has moved the solstice sunrise about a hundred times further. Stonehenge has moved about 100 m, but its solstice line has not turned.
Change in the solstice sunrise since 2500 BC: precession 0°, tilt about 1°, drift under 0.01°.
Corrections to the 2025 post
The post of 8 January 2025, "The tectonic movement of Stonehenge", reached the right conclusion: continental drift has not changed Stonehenge's solstice alignment by any measurable amount. Four of its figures need correcting:
"approximately 25 millimeters per year": about 22–23 mm a year (21.7–23.4 mm, depending on the model). "About 2 cm a year" stands.
"125 meters northward" in 5,000 years: about 100 m north-east since 2500 BC, of which about 75 m is northward. Over a full 5,000 years the total would be about 115 m.
"rotating clockwise": the Eurasian plate rotates anticlockwise about its pole in North America; at Stonehenge, about 2.5 arcseconds anticlockwise since 2500 BC.
"one-thousandth of a degree of latitude": 0.00067°.
Notes on the film
Every number in the film was computed for it from open data, with the scripts in the film's folder: the horizon from Environment Agency LiDAR, the Sun's positions with the ERFA implementation of Vondrák et al. (2011), the plate motion from the published rotation poles, and the path of the celestial pole. Published horizon profiles were used only as a cross-check. The plan of Stonehenge is from T. Daw's 3D model; the rings of Rujm el-Hiri are a schematic; maps use Natural Earth and the PB2002 plate boundaries. The film quotes only the 2024 paper's own figures for Rujm el-Hiri. Music: original.
Sources
Altamimi, Z., Métivier, L., Rebischung, P., Rouby, H. & Collilieux, X. 2017. ITRF2014 plate motion model. Geophysical Journal International 209, 1906–1912. doi:10.1093/gji/ggx136
Argus, D. F., Gordon, R. G. & DeMets, C. 2011. Geologically current motion of 56 plates relative to the no-net-rotation reference frame. Geochemistry, Geophysics, Geosystems 12, Q11001. doi:10.1029/2011GC003751
Aveni, A. & Mizrachi, Y. 1998. The geometry and astronomy of Rujm el-Hiri, a megalithic site in the southern Levant. Journal of Field Archaeology 25, 475–496. doi:10.1179/009346998792005261
Bennett, G. G. 1982. The calculation of astronomical refraction in marine navigation. Journal of Navigation 35, 255–259. doi:10.1017/S0373463300022037
Bird, P. 2003. An updated digital model of plate boundaries. Geochemistry, Geophysics, Geosystems 4, 1027. doi:10.1029/2001GC000252
Daw, T. 2025. The tectonic movement of Stonehenge. sarsen.org, 8 January 2025.
Environment Agency 2022. LIDAR Composite DTM 1 m. Contains Environment Agency data. © Environment Agency copyright and/or database right 2022. Open Government Licence v3.0.
Khabarova, O., Birkenfeld, M. & Eppelbaum, L. V. 2024. Discussion points of the remote sensing study and integrated analysis of the archaeological landscape of Rujm el-Hiri. Remote Sensing 16, 4239. doi:10.3390/rs16224239
Laskar, J. 1986. Secular terms of classical planetary theories using the results of general relativity. Astronomy & Astrophysics 157, 59–70.
Meeus, J. 1998. Astronomical Algorithms, 2nd edn. Willmann-Bell.
Rawlins, D. & Pickering, K. 2001. Astronomical orientation of the pyramids. Nature 412, 699. doi:10.1038/35089138
Ruggles, C. 1999. Astronomy in Prehistoric Britain and Ireland. Yale University Press.
Thom, A. et al. 1974. Stonehenge. Journal for the History of Astronomy 5, 71–90.
Vondrák, J., Capitaine, N. & Wallace, P. 2011. New precession expressions, valid for long time intervals. Astronomy & Astrophysics 534, A22. doi:10.1051/0004-6361/201117274

https://www.sarsen.org/2026/10/has-stonehenge-drifted-off-its-line.html

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A new henge? Lidar Lens View Adam Ibbotson and ...

2026-10-28T21:23:08Z

A new henge?

Lidar Lens View
Adam Ibbotson and ‪@WC21UKProductionsLtd‬ published a Youtube video today - below - in which they notice an unrecorded henge like shape. Of course I had to find it using the Lidar Lens, link above. Intriguing. Watch the video for more:
Adam comments:
More like “stumbled upon” / rediscovered 😅 As mentioned, Mr Phil Barrett emailed me a screenshot of one of them 4 or 5 years ago. He found they were already recorded.

https://www.sarsen.org/2026/10/a-new-henge.html

#lidarlens #lensview #henge #adamibbotson #philbarrett #intriguing

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Stonehenge Day at Springhead SP7 - 21st November Saturday 21st ...

2026-10-27T14:11:31Z

Stonehenge Day at Springhead SP7 - 21st November

Saturday 21st November is Stonehenge day, in aid of the Springhead Trust.
This is an exciting opportunity to meet up with some of the team behind the epic 11-part YouTube series Stonehenge: Access All Areas.The Definitive Series with Julian Richards, archaeologist, filmmaker and writer.
This will not be a series of lectures with a bit of time for questions, but will, like our previous successful Stonehenge days, be a genuine opportunity for discussion, to hear some of the very latest ideas about Stonehenge and its landscape, and to ask questions!
The day will start with tea/coffee at 10.00am and run through until about 4.00pm when we will conclude with afternoon tea.
Tea and coffee will be provided but lunch is self-catering. Please bring whatever you need as Springhead is in a rural location with no nearby shops or takeaways.
Tickets to Stonehenge: Access All Areas cost £50.00 per person plus a booking fee and are available here from Ticketsource.
We will also be offering an additional activity on the Sunday morning: tickets will be made available to those attending on Saturday for an optional Stonehenge landscape walk guided by Julian Richards. This is open only to those who have been part of the Saturday event. Tickets will cost £20 per person and details will be shared with those attending on the Saturday in due course.
All proceeds will go to support the work of the Springhead Trust.
Springhead
Fontmell Magna
Shaftesbury
Dorset SP7 0NU
Phone: 01747 811853
Email: info@springheadtrust.org.uk

https://www.sarsen.org/2026/10/stonehenge-day-at-springhead-sp7-21st.html

#stonehengeday #springhead #november #julianrichards #saturday #series #trust #tickets #definitiveseries #tea

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The Assize Courts, Devizes, a 3D model ...

2026-10-27T10:05:11Z

The Assize Courts, Devizes, a 3D model

https://timdaw37.github.io/assize-courts-3d
Wiltshire Museum is redeveloping the old Assize Courts. To help me visualise the plans I built a 3D model from the planning drawings so you can see the building as it is now and as it's planned. You can walk round it, look inside the courtrooms and entrance hall, and switch between the two views.
I'm an amateur, and this is version 1. It was made without specialist architectural tools, from the published planning drawings, LiDAR and open map data. It won't be perfect, but I don't think it's bad. Corrections are welcome. The interiors still need refining.
Explore it here: https://timdaw37.github.io/assize-courts-3d
The model is open source and free to reuse. The code is on GitHub at TimDaw37/assize-courts-3d under the MIT licence, so you can copy it, adapt it and share it, as long as you keep the credits. If you spot something wrong, such as a window in the wrong place, a missing detail or a height that looks off, please tell me in the comments or raise an issue on GitHub. Please keep the data credits (Environment Agency LiDAR, OpenStreetMap, Historic England and OS) when you reuse it.

https://www.sarsen.org/2026/10/the-assize-courts-devizes-3d-model.html

#assizecourts #devizes #model #wiltshiremuseum #environmentagency #historicengland #please #github #lidar #mit

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Avebury and Stonehenge in 3D, rebuilt on the LIDAR The two ...

2026-10-26T21:26:04Z

Avebury and Stonehenge in 3D, rebuilt on the LIDAR

The two landscape fly-throughs, Avebury and Stonehenge, have been rebuilt from the ground up. Both were first made on Ordnance Survey Terrain 50, a 50 m height grid with 10 m colour bands. That is fine for the shape of the downs, but nothing archaeological survives in it: Silbury Hill had to be cut out of the terrain and modelled, and every bank and barrow was drawn on top of a surface that could not show it.
Both models now stand on the Environment Agency's 1 m LIDAR terrain model. The ground is a 5 m (Avebury) or 6 m (Stonehenge) mesh for shape, shaded from the full 1 m data, so the henge ditch, the barrow groups, the lynchets and the hollow-ways are the surveyed surface rather than a drawing of it.
As it is today, and as built
Each model now has two views.
As it is today shows the LIDAR surface alone, with the barrows as rounded stumps, the Cursus banks a few centimetres high, and the roads, plantations and Larkhill camp alongside them.
As built cuts the ground away under each monument and lays a fresh-chalk reconstruction on the ground beneath. The phase buttons add each period's earthworks in turn, from the Mesolithic posts to the Middle Bronze Age fields.
The reconstructions are indicative: the plan is the surveyed one; the heights and depths are typical original dimensions, not measurements.
Avebury: what the LIDAR changed
The henge. The ditch now follows the line the LIDAR traces, 161 to 200 m from the centre, not a 210 m circle. The four causeways sit where the LIDAR ditch shallows, at bearings of about 73°, 165°, 254° and 331°, rather than exactly north, south, east and west. The ditch is still five to six metres below the bank today.
The stones. The outer circle has 98 stones (it had 44), the inner circles 27 and 29 (they had 12 each), with the Cove and the Obelisk added.
West Kennet long barrow. The surviving mound is 3.3 m high and 94 m long, and its high, broad end is to the east (bearing 85°). The earlier model had the façade at the west end.
East Kennett long barrow. It lies NW–SE, broad end to the south-east, 28 m from the OpenStreetMap position.
Round barrows. Eight of the 25 were matched to mounds that survive in the LIDAR. The rest have been ploughed out and stay at their recorded positions.
Silbury Hill is the LIDAR mound itself. The as-built view recuts its quarry ditch.
Stonehenge: monuments from Historic England's aerial mapping
The Stonehenge model goes further. Its monuments now come from Historic England's aerial investigation mapping, the bank and ditch outlines plotted from aerial photographs and LIDAR, rather than from OpenStreetMap points. That data puts 843 prehistoric bank and ditch features in the frame, sorted into the phases by monument type and period.
Early Neolithic: the cursuses, the causewayed enclosures and the long barrows.
Late Neolithic: Stonehenge, Durrington Walls, Woodhenge and Coneybury.
Beaker and Early Bronze Age: more than five hundred round barrows and ring ditches, and the Avenue.
Middle Bronze Age: field systems and lynchets.
For each mapped earthwork, the as-built view lays down a 2 m surface: the LIDAR with the surviving earthwork smoothed away, and the bank and ditch rebuilt on the mapped plan.
The Greater Cursus. The old model drew it as a straight east–west line at one northing. The mapped cursus is angled, with about 340 m of northing between its ends, and closes on the long barrow Amesbury 42 at the east. Where Historic England's mapping has gaps in the banks, the model leaves them.
The fields. The earlier model had a generated coaxial grid, labelled as indicative. That has gone. The Middle Bronze Age view now picks out only the field banks and lynchets that are mapped.
The Mesolithic posts stand at their surveyed positions in the old car park (Cleal et al. 1995). They no longer appear in the Neolithic views; they did not stand for four thousand years.
Names and phases. Bluestonehenge is now West Amesbury henge, and the Avenue is shown with the Beaker period, when it was dug.
The stones, the timber circles at Woodhenge and Durrington, Larkhill causewayed enclosure and West Amesbury henge are placed by hand from published plans. Larkhill and West Amesbury leave nothing visible in the LIDAR.
Using them
Moving: drag to turn, scroll to zoom toward the pointer, right-drag to pan; W, A, S and D walk across the ground. Double-click anywhere to move the centre of rotation there.
Readout: shows the grid reference and height of whatever you are looking at.
Save still: writes the current view as a PNG at twice screen resolution, with the labels and credits drawn in.
LIDAR grey: swaps the landscape colour for a plain hillshade.
Guided tour: still runs through each period with captions.
Vertical slider: the vertical scale is exaggerated so the chalk reads; at ×1 it is true to life.
They are heavy pages, built for a desktop or a large screen. On a phone, adding ?lite to the address loads a coarser mesh without shadows; very old phones may still not manage the Stonehenge textures.
The Stonehenge model is the phased, as-built companion to the Stonehenge landscape flyover, which stays the place for the ground as it is now, the sky and alignment checks.
Ground: Environment Agency LIDAR Composite DTM 1 m, © Environment Agency copyright and/or database right 2022 (Open Government Licence). Monuments: contains Historic England data © Historic England 2026 (Open Government Licence), aerial investigation mapping; © OpenStreetMap contributors (ODbL). Reconstructions are indicative.

https://www.sarsen.org/2026/10/avebury-and-stonehenge-in-3d-rebuilt-on.html

#lidar #stonehenge #ordnancesurvey #historicengland #rebuilt #terrain #silburyhill #environmentagency

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Rising Sea levels at Woolacombe and Saunton This is a side-hustle ...

2026-10-25T18:01:33Z

Rising Sea levels at Woolacombe and Saunton

This is a side-hustle from my Ramson Cliff erratic post. While I was looking through the 1940 German reconnaissance photos for that, I wondered whether we could show the effect of rising sea levels on the beaches at Woolacombe and Saunton.
The result is a small interactive map: Woolacombe and Saunton at 12:44 BST, 31 August 1940.
Making it a fair comparison
To make it fair, we matched the position in the tide cycle as closely as we could with modern satellite photographs, then overlaid them. Matching the tide height alone isn't enough. On a flat beach, where the water's edge appears also depends on:
Time after low water. The 1940 photos were taken about 90 minutes after low water.
Rising or falling. A falling tide leaves wet sand and pools behind it, so the edge seen from the air lags the real water level. A rising tide pushes in over drier sand.
The size of the tide. 1940 was a mid-sized tide (6.8 m range at Ilfracombe). Big spring tides move faster and push the waves further up the beach.
For example, a Sentinel-2 image from 27 September 2018 caught the sea at almost exactly the 1940 height. But the tide was falling, 100 minutes before low water, on an 8.3 m spring tide. It looks similar, but it isn't the same moment. So I kept only modern images taken on a rising tide, within 20 minutes of the 1940 timing, and with a tide range within 1.5 m of 1940's.
How the photographs were matched
The photographs were matched in the following manner:
Time. Each German frame shows the camera's clock. It ran on German summer time (CEST), one hour ahead of British Summer Time, so the Woolacombe photos were taken at about 12:44 BST. A tide model for Ilfracombe, checked against Newlyn's real 1940 record, gives the tide at that minute.
Tilt. The camera wasn't pointing straight down. It was tilted about 12°, from roughly 8 km up. I worked out the camera's position and tilt and laid each photo over the Environment Agency LiDAR ground heights, so that hills and cliffs fall in the right place.
Pinning. Each photo was then pinned to thousands of features that haven't moved since 1940: roads such as Marine Drive at Woolacombe and the Saunton road, buildings, and hedge and field corners.
Accuracy. On fixed features the 1940 photos typically sit within 2–3 m of today's imagery. Marine Drive lines up within 3 m. Among the Saunton dunes, where there is little to pin to, it is about 10 m.
Modern images. These are Sentinel-2 and Landsat scenes from 1985 to 2023, each timed against the same tide model.
What we'd expect to see
Newlyn, the gold-standard tide gauge, shows about 20 cm of sea-level rise since 1940. On Woolacombe's gentle beach, 20 cm moves the waterline only about 8 m. On the flatter sand at Saunton the LiDAR puts it at around 20–30 m.
Conclusion
On these sorts of beaches it's invisible. Sand moving about and the natural spread of the waterline swamp it. On 1940 film, wet sand and shallow water look alike, so the 1940 edge alone can shift by up to 50 m depending on how it's read. Of 106 modern Landsat and Sentinel-2 readings, 27 match the 1940 tide. On those, the water's edge sits a median of −0.08 m from the predicted tide at Woolacombe and +0.16 m at Saunton. Neither shows a trend that stands out from the noise. The rise is real, but you measure it with a tide gauge, not on a sandy beach.
Explore the map. 1940 photos: U.S. National Archives, RG 373. Contains modified Copernicus Sentinel data. LiDAR © Environment Agency (OGL).

https://www.sarsen.org/2026/10/rising-sea-levels-at-woolacombe-and.html

#saunton #sealevels #risingsea #german #summertime #marinedrive #ramsoncliff #bst #ilfracombe #modern

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Cheddar to Bath , via Bristol November 1940 Aerial Film The ...

2026-10-25T17:27:30Z

Cheddar to Bath , via Bristol November 1940 Aerial Film

The previously blogged Wiltshire run is the second half of a much longer sortie. NARA holds 254 prints from the two cameras under box GX 10484, and the item records place them on a single loop. The aircraft crossed the Devon coast at Sidmouth (L 1), flew north past Honiton to the Blackdown Hills, then north-east by Taunton, Bridgwater and the Levels to Cheddar, the Mendips and Bristol. North of Filton it turned east and south, and came back by Doynton and Keynsham to Bath and Freshford, where the Wiltshire frames begin at L 109. After Wiltshire it crossed the New Forest and left the coast at Barton-on-Sea (L 148): some 255 km on the long-lens camera alone.
The film above joins the long-lens frames from Cheddar to Freshford, L 56 to L 108. Fair-weather cumulus covers much of the Mendips, Dundry and Bristol (L 62–88); the ground still matches between the clouds, so the frames join, but the clouds sit far above the ground and shift between exposures. Exposure 86 and exposure 91 are not in the NARA set. L 86 is bridged by a small overlap between 85 and 87; L 91 leaves a short break in the film.
Over Bristol the frames come closer together. Over the Mendips successive frames are about 1,000 scanned pixels apart, over the city about 600, and the camera clocks agree: roughly one exposure every 20 seconds from L 56 to L 76, against one every 10 seconds from L 76 to L 85 (minute-hand readings by eye, good to about half a minute). NARA lists L 87–92, north of Filton, as obliques, although at least L 88 appears near-vertical; the label may reflect the aircraft banking into the turn. No record found names a target.
Bath is clear. On L 105 the Royal Crescent and the Circus stand out above Royal Victoria Park, seventeen months before the air raids of April 1942.
Bath on L 105, 29 November 1940: the Royal Crescent (centre) facing Royal Victoria Park, with the Circus above it. Turned to read roughly north-up. Luftwaffe, NARA RG 373, GX 10484.
Bristol through broken cloud, Bedminster to Ashley Down, L 76–84.
Notes on the film
The landscape film runs at about four times real speed and is turned so that the aircraft flies left to right. Each frame is captioned with its exposure number, NARA's nearest place name and its clock reading. The Cheddar to Bath film is a director's cut, without captions, and ends where the Wiltshire film begins. The music is original.
Sources
National Archives and Records Administration. German Flown Aerial Photographs, 1939–1945. RG 373, series NAID 306065; file units GX 10484 SG. catalog.archives.gov/id/306065
National Archives and Records Administration. Target Dossiers Pertaining to the British Isles, 1938–1945. RG 242, series NAID 3371016. catalog.archives.gov/id/3371016
National Collection of Aerial Photography. German Air Force (Luftwaffe), GB 551 NCAP/4. ncap.as.atlas-sys.com
Luftwaffedata Wiki. Aufkl. Gr. 123 1940. luftwaffedata.co.uk
Luftwaffedata Wiki. Aufklärungsgruppe Ob.d.L. luftwaffedata.co.uk
Daw, T. 2026. The Luftwaffe's Wiltshire. sarsen.org; map at wiltshire-luftwaffe.netlify.app
All photographs: Luftwaffe, 29 November 1940; US National Archives, RG 373, GX 10484, listed as Use: Unrestricted. Frame matching, measurements and film: T. Daw. Methods and scripts: github.com/TimDaw37/wessex-films.

https://www.sarsen.org/2026/10/cheddar-to-bath-via-bristol-november.html

#bristolnovember #film #bath #wiltshire #cheddar #nara #aerialfilm #royalvictoria #royalcrescent #victoriapark

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Looking for the Ramson Cliff Erratic in 1940 - the film The ...

2026-10-25T12:51:43Z

Looking for the Ramson Cliff Erratic in 1940 - the film

The Ramson Cliff boulder has had me hooked for over a year now (the mystery, the 2025 visit, the second thin section and last month's post), and the full story is in the paper in Quaternary Newsletter 167. One question kept nagging at me. The stone was found in 1969 at SS 4356 4070, out in the field on Baggy Point, and moved to the field edge in the early 1970s. Was it already sitting there in 1940, and would a wartime aerial photograph show it?
So I flew in to have a look, using a Luftwaffe reconnaissance photograph taken over North Devon in the summer of 1940.
How I made it
The photographs come from Luftwaffe sortie GX 10006 SD, flown on 31 August 1940. Each frame has the camera's clock photographed in the corner. The clock in the neighbouring frame reads 12:45 BST, which puts the frame over the find spot at about the same moment. I lined the frames up against the modern map, tightening the fit around Baggy Point using the field banks that show on the Environment Agency LiDAR. Then I stitched them into a mosaic and flew a virtual camera in from the south over Croyde, descending and tilting down until it looks straight down on the target.
On the approach: the 1940 fields of Baggy Point, built from sortie GX 10006 SD.
The limit is resolution. The National Archives scans of these frames come out at about 1.5 m per pixel on the ground. The boulder is 105 x 55 x 38 cm and weighs 378 kg, so it is smaller than a single pixel. I never expected to see the stone itself. What I was looking for were the things a big stone in a field does to the land around it: livestock tracks converging on it, a trampled or poached patch, ploughing that bends round it, or an unploughed island left where the plough couldn't go.
Over the target: the circle marks the 1969 find spot, SS 4356 4070, on the 31 August 1940 photograph.
What it shows
Honestly, nothing. In 1940 the find spot lies in a strip of grass inside the cliff-top boundary. With the contrast pushed up there are no tracks running to it, no worn patch, and no sign of cultivation avoiding it. The other photographs I have looked at, GX 11967 (23 March 1941) and RAF 106G/LA/132 (14 February 1945), are no clearer. That doesn't prove the stone wasn't there: a stone smaller than a pixel in a grass field could easily leave no trace. But the wartime air photos can't settle it either way.
The film ends on the LiDAR, which picks out the cliff-top field edge where the stone sits today.
Credits
Aerial photographs: US National Archives, Record Group 373. LiDAR: Environment Agency, contains public sector information licensed under the Open Government Licence v3.0.

https://www.sarsen.org/2026/10/looking-for-ramson-cliff-erratic-in.html

#ramsoncliff #clifferratic #baggypoint #quaternarynewsletter #environmentagency #nationalarchives #film #luftwaffe #august #northdevon

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LiDAR Lens Anglesey LiDAR Lens Ynys Môn puts the whole of ...

2026-10-24T19:15:47Z

LiDAR Lens Anglesey

LiDAR Lens Ynys Môn puts the whole of Anglesey in 1 m LiDAR into a fast, free viewer that works as well on a phone in a field as on a desktop. The Welsh Government's LiDAR covers essentially the entire island, and every tile is stored with the lens, so it loads quickly wherever you are. Bryn Celli Ddu sits in its landscape, Barclodiad y Gawres crowns its headland, the walls and streets of Caergybi (Holyhead) show through, and the old hut circles and fields on Mynydd Tŵr (Holyhead Mountain) leap out of the hillside. Place names are Welsh first, with English in brackets, and all 147 of Cadw's scheduled monuments on the island are marked and linked. There is no login, no account and no adverts.
How it works
Pan and zoom across the island, or use Go to box to jump to a place or grid reference. On a phone, Use my location puts you on the map where you are standing, which is handy in the field. The 146 place names come from the Welsh Language Commissioner's list of standardised Welsh place names, such as Biwmares (Beaumaris) and Llangefni. Click a scheduled monument to open its Cadw report, and follow the links out to Archwilio and Coflein for the wider historic environment record.
Fair use
No historic environment record data is copied into the lens; it links to Archwilio and Coflein, which remain the places to look things up. Please respect landowners, and remember that scheduled monuments are protected by law. Seeing something in the LiDAR is not permission to go and look.
Credits
LiDAR: Welsh Government 1 m DTM (DataMapWales), Open Government Licence v3
Place names: Welsh Language Commissioner, list of standardised Welsh place names
Scheduled monuments: Cadw, Open Government Licence
Links: Archwilio and Coflein (RCAHMW)
For England and Wales as a whole, and the other lenses, see lidarlens.sarsen.org. The code is on GitHub. Comments and anything interesting you spot are welcome below.

https://www.sarsen.org/2026/10/lidar-lens-anglesey.html

#lidarlens #welsh #welshgovernment #welshlanguage #anglesey #governmentlicence #opengovernment #languagecommissioner #ynysmon #scheduled

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LiDAR Lens Ynys Môn Mae LiDAR Lens Ynys Môn yn dangos Môn ...

2026-10-24T18:41:19Z

LiDAR Lens Ynys Môn

Mae LiDAR Lens Ynys Môn yn dangos Môn gyfan mewn LiDAR 1 m, mewn gwyliwr cyflym am ddim sy'n gweithio cystal ar ffôn mewn cae ag ar gyfrifiadur. Mae LiDAR Llywodraeth Cymru yn cwmpasu'r ynys gyfan bron, ac mae pob teil yn cael ei gadw gyda'r lens, felly mae'n llwytho'n gyflym ble bynnag yr ydych. Mae Bryn Celli Ddu i'w weld yn ei dirwedd, Barclodiad y Gawres ar ei bentir, strydoedd a muriau Caergybi yn dod i'r golwg, a'r cytiau crwn a'r hen gaeau ar Fynydd Tŵr yn neidio allan o lethrau'r mynydd. Mae'r enwau lleoedd yn Gymraeg yn gyntaf, gyda'r Saesneg mewn cromfachau, ac mae pob un o 147 heneb gofrestredig Cadw ar yr ynys wedi'u marcio, gyda dolen i'w hadroddiad. Does dim angen mewngofnodi, dim cyfrif a dim hysbysebion.
Sut mae'n gweithio
Symudwch a chwyddwch ar draws yr ynys, neu defnyddiwch y blwch Go to i neidio i le neu gyfeirnod grid. Ar ffôn, mae Use my location yn eich rhoi ar y map yn y fan lle rydych yn sefyll, sy'n ddefnyddiol yn y maes. Daw'r 146 enw lle o restr Comisiynydd y Gymraeg o enwau lleoedd safonol, er enghraifft Biwmares (Beaumaris) a Llangefni. Cliciwch ar heneb gofrestredig i agor ei hadroddiad gan Cadw, a dilynwch y dolenni i Archwilio a Coflein am y cofnod amgylchedd hanesyddol ehangach.
Defnydd teg
Nid oes unrhyw ddata o'r cofnod amgylchedd hanesyddol wedi'i gopïo i'r lens; mae'n cysylltu ag Archwilio a Coflein, sy'n parhau i fod y lle i chwilio. Parchwch dirfeddianwyr, a chofiwch fod henebion cofrestredig wedi'u diogelu gan y gyfraith. Nid yw gweld rhywbeth yn y LiDAR yn rhoi caniatâd i fynd i edrych arno.
Cydnabyddiaeth
LiDAR: DTM 1 m Llywodraeth Cymru (MapDataCymru), Trwydded Llywodraeth Agored f3
Enwau lleoedd: Comisiynydd y Gymraeg, rhestr o enwau lleoedd safonol Cymru
Henebion cofrestredig: Cadw, Trwydded Llywodraeth Agored
Dolenni: Archwilio a Coflein (CBHC)
Am Gymru a Lloegr gyfan, a'r lensys eraill, ewch i lidarlens.sarsen.org. Mae'r cod ar GitHub. Croeso i chi adael sylwadau, ac unrhyw beth diddorol a welwch, isod.

https://www.sarsen.org/2026/10/lidar-lens-ynys-mon.html

#ynysmon #lensynys #lidarlens #llywodraethcymru #trwyddedllywodraeth #mae #enwau #archwilio #coflein #gymraeg

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Stanton Moor LiDAR Lens ...

2026-10-24T14:04:35Z

Stanton Moor LiDAR Lens

https://www.stonetemplegardening.com/stg-lidar-lens-stanton-moor
Stone Temple Gardening has used the free GitHub code to create a great looking LiDAR Lens for Stanton Moor, have a look. Great job.

https://www.sarsen.org/2026/10/stanton-moor-lidar-lens.html

#stantonmoor #lidarlens #templegardening #stonetemple #great #github

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Twice into the guns: the Royal Wiltshire Yeomanry at El Alamein ...

2026-10-23T09:24:40Z

Twice into the guns: the Royal Wiltshire Yeomanry at El Alamein

This post is the companion to the short film Twice into the guns. The film follows the Royal Wiltshire Yeomanry through the two attacks it made at the Second Battle of El Alamein, over the ground as it lies today. The sources, figures and maps behind it follow.
The regiment
The Royal Wiltshire Yeomanry was raised in 1794 and kept its horses until 1941. Converted to tanks, it went to Egypt in May 1942 with the 3rd Hussars and the Warwickshire Yeomanry as 9th Armoured Brigade (Brigadier John Currie), placed under the 2nd New Zealand Division (Lieutenant-General Bernard Freyberg) for the coming offensive. For Operation Lightfoot the regiment, under Lieutenant-Colonel Peter Sykes, held 10 Shermans, 14 Grants and 13 Crusaders; six of the Crusaders were detached to go forward with the 21st and 22nd New Zealand Battalions (US Army 2006, App. J, from the regimental war diary).
The ground
The Alamein line from the air: the Axis minefields as mapped at daybreak on 24 October 1942, Miteiriya and Ruweisat Ridges, the Qattara Depression on the horizon.
Copernicus GLO-30, heights × 8.
The northern Alamein position is close to flat. Most of it lies between 15 and 45 m above sea level, and Miteiriya Ridge, the New Zealand objective on the first night, stands only 5 to 6 m above the desert around it (US Army 2006, App. H). The terrain views in the film are rendered from the Copernicus GLO-30 elevation model, with heights exaggerated eight times so that the ridges show at all. The model records the ground surface today, so modern roads, pipelines and coastal building appear in it.
Both armies lay behind deep belts of mines and wire. The Axis belts shown in the film are those drawn on the New Zealand official history's map of 30 Corps at daybreak on 24 October (Walker 1967), transferred to the modern terrain by matching the map's trig points and stations to the elevation data. The fit is good to roughly a kilometre, and every position in the film should be read at that resolution.
The first attack: 23–24 October
First light, 24 October: the regiment behind 22 NZ Battalion, and elements beyond the final objective, from 2 NZ Division's map of the sector (Pitt 1946, Map No. 5).
The barrage opened at about 9.30 pm and, in Major Hubert Blount's words, "continued to fire rapid without a break until about 4.30 in the morning" (letter, in Keoghane 2021, p. 131). New Zealand sappers cleared lanes through two Axis minefields: all four lanes through the first were open by 2.30 am and the second by 5 am (US Army 2006, App. K). "There was a good moon during the early part and in the leading tank it was quite easy to see the markings of the lane," Blount wrote.
B Squadron, in Crusaders, was reduced to two tanks by mines (Keoghane 2021, p. 129). A Squadron, with the new Shermans, and C Squadron, in Grants, came up on 22 Battalion's route, where the battalion commander had his men search and mark a mine-free track through their positions. "Not long after six o'clock, tanks of the leading squadron had been guided over the ridge," and the second heavy squadron followed, making the Royal Wiltshire Yeomanry "the first, and only, regiment to break out beyond the infantry's final objective on this first morning of the Alamein battle" (Walker 1967, p. 274). 2 NZ Division's own map of the sector at first light shows the regiment just behind 22 Battalion and "Elements R. Wilts Yeo" beyond the final objective (Pitt 1946, Map No. 5).
The counter-attack came in the morning. "We set the first line of six on fire when they were about 1500 yards from us," Blount wrote (p. 132). The Commanding Officer was wounded. Tanks immobilised on mines drew fire onto the New Zealand infantry, and shortly after midday the four remaining runners were withdrawn into cover. Casualties to that time were 10 killed or missing and 32 wounded, including the Commanding Officer and seven other officers (Walker 1967, p. 302). Next day the regiment was taken out of the line and its last tanks were handed to the other two regiments (Walker 1967, p. 305).
Rebuilt
Over the following week the regiment took over repaired replacement tanks, "in a shocking state" (Keoghane 2021, p. 130). The brigade, down to 36 runners on the evening of 25 October, was built back to 80 Shermans and 52 Crusaders before the second attack (Walker 1967).
The second attack: 1–2 November
2 November: the regiment's route to the start line (the 863 grid line) and across the Rahman Track. Positions from the official history's map of Operation Supercharge.
Operation Supercharge gave 9th Armoured Brigade the hardest task of the offensive: to cross the infantry's new line and break the last anti-tank gun line along the Rahman Track, so that 1st Armoured Division could pass through. Montgomery said he was prepared for heavy casualties in the brigade (Walker 1967, pp. 391–2).
The brigade formed up near El Alamein station with 105 tanks and set off at about 7 pm on 1 November. The night was moonless and the tracks had been ground to powdery dust (p. 392). The Wiltshires followed the Hussars along Sun track and Boomerang track, halting to refuel at 1.45 am (pp. 392–3). On the way a field of British mines, laid irregularly, held them up until 6 New Zealand Field Company cleared it; the brigade's report praised the sappers' work as "beyond all praise" (US Army 2006, App. L). The New Zealand engineers marked the route with green lamps every tenth of a mile.
The attack was put back half an hour. At 6.15 am the regiment crossed the start line with 33 tanks: the twelve Crusaders of B Squadron in the lead, and C, Headquarters and A Squadrons level in line a short way behind (Walker 1967, pp. 393–4). The Crusaders overran gun pits and crossed the Rahman Track, marked by its line of telegraph poles, into heavier guns sited further west. The heavy squadrons came under fire as they reached the track and were ordered hull-down; A and C Squadrons engaged on the flanks (Keoghane 2021, p. 130). With wireless contact to B Squadron lost, the commanding officer had the two heavy squadrons lay smoke to cover its withdrawal. According to survivors, all but one of B Squadron's Crusaders went up in flames, after which the enemy switched his fire to the heavy squadrons (Walker 1967, p. 394). By about 8 am the regiment had nine tanks (p. 396).
Together the 3rd Hussars and the Wiltshires were credited with overpowering some 35 anti-tank guns, mainly Italian 47 mm and German 50 mm (p. 395). The brigade began the day with 94 tanks across the start line and ended it with about 24 fit to fight; the tank regiments had 163 casualties (p. 401), among them Trooper Herbert Daw of C Squadron, the film-maker's father, captured that morning after his tank was knocked out. The gun line, manned mainly by German gunners and short of ammunition, was close to breaking. On 4 November Tell el Aqqaqir was occupied unopposed and the Axis army was withdrawing (pp. 418–22). On 5 November the Commanding Officer wrote to all ranks: "This action will be recorded in the annals of regimental history, and the epic of B Squadron will live for all time" (Keoghane 2021, p. 130).
The fernleaf
Under 2nd New Zealand Division the regiment painted the Division's fernleaf on its vehicles. When it left Italy for England in September 1944, Lieutenant-Colonel Ian Lloyd wrote to General Freyberg asking whether it might go on wearing the emblem. Freyberg replied from Headquarters, 2 N.Z. Division, on 22 November 1944: "we will be very proud to know you are continuing to wear the fernleaf as a reminder of Alamein days together." No association in the war, he wrote, "was happier than that between the Officers and men of the 9th Armoured Brigade and ours in the difficult days at Miteiriya Ridge and in the battle to break out." Of 2 November he added: "Your gallant advance that morning, though at great cost, broke the gun line and was the turning point in one of the most decisive battles of the war." He called the brigade's men "honorary New Zealanders" (letter printed in Pitt 1946). The Wiltshire squadrons of the Royal Wessex Yeomanry, B and Y, still wear the fern on their parade uniforms (Royal Wessex Yeomanry).
What is not settled
Times. Walker has the regiment's four runners pulled into cover shortly after midday on 24 October; Keoghane has Major Gibb ordering the remaining tanks back at 6 pm. On 2 November Walker gives permission to withdraw at 9.10 am; Keoghane has the regiment withdrawn at 4 pm with four tanks. These may be different moves; no source says so.
Positions. All are taken from 1942 maps drawn at small scale and fitted to modern elevation data; treat them as good to about a kilometre. The lanes in the film are a diagram, after 2 NZ Division's own diagram of its routes.
"100 per cent casualties." The often-quoted order to accept them appears in the New Zealand engineers' history but has not been traced to a primary document, and is not used.
The war diary. The regiment's war diary for 1942 (The National Archives, WO 169/4501; a copy at the Tank Museum) has not yet been read for this post.
Sources
R. Walker, Alam Halfa and Alamein, Official History of New Zealand in the Second World War 1939–45 (Wellington: Historical Publications Branch, 1967). NZETC text.
US Army Night Vision and Electronic Sensors Directorate, Breaching the "Devil's Garden": Operation Lightfoot, the Second Battle of El Alamein, 23 October 1942 (Appendices), AMSRD-CER-NV-TR-220A (Fort Belvoir, 2006).
S. Keoghane, Primus in Armis: An Illustrated History of the Royal Wiltshire Yeomanry (2021), ch. 6 and "Yeomanry Tales".
P. W. Pitt, Royal Wilts: The History of the Royal Wiltshire Yeomanry 1920–1945 (1946), maps, including 2 NZ Division Map No. 5 and the route of the regiment in Operation Supercharge.
The Eighth Army, September 1941 to January 1943 (HMSO, 1944).
M. Carver, El Alamein (London: Batsford, 1962), maps by Arthur Banks: the mined and defended areas of 23 October and the line of Miteiriya Ridge, redrawn on the terrain.
Terrain: Copernicus GLO-30 DEM, © DLR e.V. 2010–2014 and © Airbus Defence and Space GmbH 2014–2018, provided under COPERNICUS by the European Union and ESA.

https://www.sarsen.org/2026/10/twice-into-guns-royal-wiltshire.html

#royalwiltshire #wiltshireyeomanry #newzealand #alamein #october #warwickshireyeomanry #army #zealandbattalions #guns #axis

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LiDAR Lens - the free comprehensive LiDAR viewer for England and ...

2026-10-22T19:03:27Z

LiDAR Lens - the free comprehensive LiDAR viewer for England and Wales

LiDAR Lens is, I think, the best and most complete free LiDAR tool there is for England and Wales. Every square metre of both countries' 1 m LiDAR is there, live, in a lens you drag across the map. You can light it from any angle, exaggerate it, and switch between hillshade, multi-direction hillshade, slope, local relief, sky-view factor, aspect and red relief, until faint banks, ditches, barrows and lost field systems jump out. Click any spot and it tells you the ground's measurements and the recorded sites nearby, with links straight to the records. Old OS maps, aerial photos and modern maps sit underneath for comparison. It works on a phone in the field as well as on a desktop. It costs nothing, there is no login, no account, and no adverts.
How it works
Type a place, postcode or grid reference into the search bar, or tap ◎ Me to go to where you are standing. Drag and resize the lens, and use the sliders for sun angle, exaggeration and contrast. "What’s here?" pins a point, gives its grid reference to copy, and lists nearby records: Historic England in England, and Cadw and Coflein in Wales. The profile tool draws a height section between two clicks, and Share copies a link to the exact view.
Fair use
The LiDAR is fetched live from the Environment Agency and the Welsh Government, through a Cloudflare cache. Each piece is fetched once and shared by everyone, the lens only asks for what is under it, and it backs off if a service is busy. The Environment Agency has confirmed it is happy for the data to be used this way, under its fair use policy.
Please respect landowners, and remember that scheduled monuments are protected by law. Seeing something in the LiDAR is not permission to go and look.
Credits
LiDAR, England: Environment Agency, Open Government Licence
LiDAR, Wales: Welsh Government (DataMapWales), Open Government Licence
Recorded sites, England: Historic England open data, Open Government Licence
Recorded sites, Wales: Cadw, and the National Monuments Record of Wales (Coflein, RCAHMW), Open Government Licence
Historic maps: reproduced with the permission of the National Library of Scotland, CC-BY
Background maps: OpenTopoMap (CC-BY-SA), map data © OpenStreetMap contributors; aerial imagery © Esri, Maxar, Earthstar Geographics
The code is open on GitHub. Comments and anything interesting you spot are welcome below.

https://www.sarsen.org/2026/10/lidar-lens-free-comprehensive-lidar.html

#england #wales #governmentlicence #historicengland #opengovernment #lidarlens #environmentagency #welshgovernment #licencerecorded #free

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Make your own LiDAR Lens You do not need to be a programmer. An ...

2026-10-22T09:03:51Z

Make your own LiDAR Lens

You do not need to be a programmer. An AI helper does the technical work; you make a few choices and open one free account.
What you get
A LiDAR Lens is a free map in your browser that takes away the trees and crops, so the shape of the ground shows: old banks, barrows, field systems, hollow ways. Drag a circular lens over an old Ordnance Survey map and the bare ground appears inside it. Turn the sun, change how the ground is drawn, and tap a spot to see what is recorded there. It works on a phone.
There is one for Wiltshire. On 21 October 2026 an AI helper built another, for the henges of the Ure and Swale valleys in North Yorkshire: 700 km² from the Thornborough henges to the Devil's Arrows, in about an hour, from the idea alone.
Four steps
Get an AI helper that can do work on a computer for you, not just chat. Claude and Grok have both built a Lens. For most people the paid AI plan is the only cost.
Give it one message. Copy the message below, change the area to yours, and send it.
Make a few choices. It may ask you, or choose for you: which area, whether the map is open to everyone or behind a password, and which old maps go underneath.
Open one free account. To put your map online it will ask you to open a Cloudflare account. Cloudflare asks for a card when you switch on its storage, but a county-sized map fits in the free allowance.
Then let it work. The 700 km² Ure map took about an hour. A whole county takes longer: most of a day, mostly unattended. Start with something small, such as your parish or a valley.
The message to copy
Please read the instructions at https://github.com/TimDaw37/lidar-lens and build me a LiDAR Lens for [your area]. I am not a programmer: explain each step in plain English, and ask me before anything that costs money or needs an account.
For your AI helper: the build guide is PROTOCOL.md in the lidar-lens code (MIT licence). Configs for Wiltshire and a blank template are in configs/. Use open data only and keep showGuess:false on a public site.
What it costs
The AI helper: a paid plan. Prices vary and change.
Cloudflare (putting the map online): usually nothing. The free allowance is 10 GB of storage (a county takes about 3–4 GB) and 100,000 requests a day, plenty for a club, a society or a village. A busy public map might need the paid plan, about $5 a month.
Your computer: nothing extra, but a whole county needs about 30 GB of free space and a good connection. Some of the work can be done on the AI's own computer instead.
The LiDAR and the old maps: free (Environment Agency, Open Government Licence; National Library of Scotland, CC-BY).
Not in England?
The Environment Agency's 1 m LiDAR covers England. Wales has its own free LiDAR from Natural Resources Wales (DataMapWales), and Scotland from the Scottish Remote Sensing Portal. The build guide says how to use them.
Two rules
Open records only. National records from Historic England and OpenStreetMap are open. Your county's own Historic Environment Record is not: it needs the county's permission before any of it goes on a public map. Linking to it is fine.
Report, don't publish. If you spot something new, tell your county's Historic Environment Record. Don't post maps of possible new sites: they help illegal metal detectorists. Most land is private, and scheduled monuments are protected by law.
Have a go
If it gets stuck, tell it what went wrong and let it try again. Start small, and share the link when it works.
Sources
LiDAR Lens code and build guide: github.com/TimDaw37/lidar-lens (MIT licence).
Environment Agency, LIDAR Composite DTM 1 m (Open Government Licence).
Cloudflare, R2 pricing and Workers pricing, checked 21 October 2026.
National Library of Scotland georeferenced OS maps (CC-BY).
The same guide on GitHub: READ-ME-FIRST.

https://www.sarsen.org/2026/10/make-your-own-lidar-lens.html

#lidarlens #open #make #environmentagency #own #england #ordnancesurvey #cloudflare #ure #wiltshire

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The largest henge in the world? This post is the companion to the ...

2026-10-21T09:17:02Z

The largest henge in the world?

This post is the companion to the short film The largest henge in the world?, which revisits a post from October 2016 with fresh LiDAR. The measurements, sources and caveats follow.
The earthwork
In west Wiltshire, on private farmland with no public footpath, a bank and ditch enclose two ploughed fields beside a chalk river. Trees grow along most of the bank, so from the air it looks like a ring of woodland round the fields. The interior is ploughed out, but under the trees the bank and ditch are still impressive. In April 2016 I walked round it; the photographs here are from that walk.
Environment Agency first-return LiDAR: the trees on the bank.
The ditch in woodland, April 2016.
How big?
Traced along the outer edge of the bank on the Environment Agency's LIDAR Composite DTM at 1 m (2022), the earthwork encloses 23.2 ha, with a perimeter of 1.83 km and an extent of 640 × 530 m. A trace along the inner edge of the bank would give about 2–3 ha less. The 2016 post gave 23 ha.
For comparison, Historic England gives Durrington Walls "a roughly circular area of 19ha", c. 490 m north–south by 468 m east–west (list entry 1009133), and Marden "an irregular area of approximately 15ha", a maximum of 530 by 360 m (list entry 1014617). Both are overall figures, so the outer-edge measurement is the like-for-like one. In the film the two are drawn as ovals of those published dimensions, not as traced outlines.
Same scale: the traced earthwork (red) with ovals of the published sizes of Durrington Walls (gold) and Marden (blue).
The ditch is inside the bank
A henge is defined by its ditch lying inside its bank, the reverse of a defended enclosure. Height profiles across the earthwork on the LiDAR show the same pattern on the west, south and east sides: an outer slope, the bank, then a hollow on the inner side where the ditch has silted up, before the level interior. On the west side the bank stands about 3 m above the ground outside and the silted ditch lies about 0.6 m below the interior. On the north the earthwork follows the edge of the river terrace, which falls about 10 m to the floodplain; there the river forms part of the boundary, as the Avon does at Marden, where "the fourth side of the enclosure is formed by the edge of the floodplain" (Historic England 1014617). A few small quarries cut into the ditch.
Bare-earth LiDAR, lit from the north-north-east for relief.
Profile across the west side, from the LiDAR. Diagram, height ×10.
What it has been called
The Wiltshire and Swindon Historic Environment Record lists it as a Romano-British settlement (MWI1116). Sir Richard Colt Hoare (1821) described it as a Roman station, with very black soil and much pottery. A local history of 1879 records iron armour, pottery and a large number of coins in three urns found in 1792; thirteen coins and a New Forest ware thumb pot are in Salisbury Museum. When the Ordnance Survey visited in 1966 they favoured a medieval enclosure. The record also lists an evaluation excavation in 2012, whose report I have not been able to find.
Roman finds show that the place was used in the Roman period. They do not date the bank.
A henge
David Field and David McOmish, in Neolithic Horizons (2016), and I read it as a henge, probably of a similar date to Marden. It has never been dated. Until it is, the henge reading rests on its form: a very large enclosure, ditch inside bank, with a river along one side.
Notes on the film
"The largest henge in the world" is a deliberate flourish. Henges are almost unknown outside Britain and Ireland, so the title is easily won; the real comparison is with Durrington Walls and Marden.
All LiDAR images are from the Environment Agency's LIDAR Composite DTM and First Return DSM at 1 m, under the Open Government Licence. Relief is shaded with the sun moved for clarity; the section diagram exaggerates height ×10.
The trace of the earthwork is by eye on a hillshade (27 points).
Sources
Field, D. and McOmish, D. 2016. Neolithic Horizons: Monuments and Changing Communities in the Wessex Landscape. Stroud: Fonthill.
Historic England. List entry 1009133, Durrington Walls; list entry 1014617, The Hatfield Earthwork, Marden.
Hoare, R. C. 1821. The Ancient History of Wiltshire, vol. II. London. (Via the HER.)
Wiltshire and Swindon Historic Environment Record, MWI1116.
Environment Agency. LIDAR Composite DTM 1 m and First Return DSM 1 m. Open Government Licence.

https://www.sarsen.org/2026/10/the-largest-henge-in-world.html

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A LiDAR Lens for the Ure henges: Thornborough to the Devil's ...

2026-10-21T08:51:48Z

A LiDAR Lens for the Ure henges: Thornborough to the Devil's Arrows

After the Wiltshire LiDAR Lens, I wanted to look at the other great henge landscape, in North Yorkshire. So there is now a second one, free and with no login: the LiDAR Lens for the Ure henges.
What it covers
It uses the Environment Agency's 1 m LiDAR composite terrain model for a strip about 19 km by 37 km (703 km²), from Scorton and Catterick in the north down to the Devil's Arrows at Boroughbridge. The sites include:
the three Thornborough henges
the Nunwick, Hutton Moor, Cana Barn and Sinderby henges
the Devil's Arrows
Catterick and the Scorton cursus
One to look at is Langthorpe, just north-west of the Devil's Arrows. YAAM has drawn attention to earthworks there as a possible "super-enclosure". Their age and purpose are unknown. I have marked the spot where I think it shows in the LiDAR: see the Langthorpe view and judge for yourself.
How to use it
A circular lens sits on the aerial photo. Drag it about and resize it to see the bare ground underneath, drawn as hillshade, slope, local relief, sky-view factor or red relief. Low sun and some vertical exaggeration bring out the faint banks and ditches.
Click "What’s here?" and then a spot. The panel gives plain measurements of the ground there and lists nearby recorded sites, with links to the records. It does not guess what a feature is. That is left to you.
Credits
LiDAR: Environment Agency, Open Government Licence
Recorded sites: Historic England open data (scheduled monuments, listed buildings, aerial investigation mapping), Open Government Licence
Map data © OpenStreetMap contributors
Historic maps: reproduced with the permission of the National Library of Scotland, CC-BY
There is no North Yorkshire HER data in it. Instead, the "What’s here?" card links out to Heritage Gateway for the spot you clicked. Please respect landowners, and remember that scheduled monuments are protected by law.
The code is on GitHub if you would like to build one for your own patch. Comments and anything interesting you spot are welcome below.

https://www.sarsen.org/2026/10/a-lidar-lens-for-ure-henges.html

#lidarlens #urehenges #arrows #thornborough #arrowscatterick #northyorkshire #environmentagency #wiltshirelidar #governmentlicence #opengovernment

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Historic Wales: a first look at the new map portal for Welsh ...

2026-10-20T13:27:33Z

Historic Wales: a first look at the new map portal for Welsh heritage

I spend most of my time peering at Wiltshire, at sarsens, long barrows and LiDAR hillshades, so it's good to look over the border now and then and see how our Welsh neighbours do things. The new Historic Wales portal is in public beta until 1 December 2026, and its team is asking for feedback. So I've had a good look round.
What it is and who's behind it
Historic Wales calls itself "the map enabled portal for historic environment information in Wales". It's run by the Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW) and built on Esri's ArcGIS Hub and Experience Builder. What makes it worth having is that it brings the main Welsh heritage datasets together in one map:
Cadw (cadw.gov.wales): Scheduled Monuments (I counted 4,236 records), Listed Buildings, Registered Historic Parks & Gardens and Designated Wrecks.
Heneb (heneb.org.uk), the new body that now runs the regional Historic Environment Records: the HER of Wales, a huge 271,366 points, each linking to its Archwilio record.
RCAHMW: the National Monuments Record of Wales, split into terrestrial and maritime layers, with each point linking to Coflein.
Think of it as Wales's answer to England's Heritage Gateway and Historic England's National Heritage List map, but on one map. That's the bit I envy. In Wiltshire I have the scheduling on one site, the HER on another and the old maps on a third.
The historic maps are the real treat
The highlight for me is the "Historic Mapping" theme. RCAHMW is working with regional archives and the National Library of Wales to digitise and georeference historic maps, and the beta already includes:
Enclosure maps, funded by the Welsh Government. Breconshire, Carmarthenshire, Denbighshire, Flintshire, Glamorgan, Monmouthshire, Montgomeryshire and Pembrokeshire are already in, with the rest promised. You can lay Brecon Forest in 1819 or Malltraeth Marsh in 1861 straight over today's map.
Admiralty charts from the UK Hydrographic Office, covering Milford Haven in 1830, the Swellies in 1872, Holyhead harbour and dozens more. Together they make up a new Maritime map.
6-inch Ordnance Survey maps from 1868 to 1892, courtesy of the National Library of Scotland, plus a promise of the 25-inch first edition. Anglesey and Flintshire are said to be online already.
Historic county and civil parish boundaries for 1860–89 and 1889–1906. They're really handy, because so many old records are filed by the pre-1974 counties.
One tip, because it caught me (and others) out: ticking "Historic Mapping" on its own shows nothing. Every map sheet starts switched off, so expand the group, then the county or chart set, and tick an individual sheet. Each one only covers its own patch, so zoom to it. Once you know that, it all works nicely. The 1880s 6-inch sheet around Pentre Ifan is crisp right down to field level.
There's a swipe tool for comparing old and new maps, a measure tool, a choice of basemaps, layer reordering and transparency, and a table view. Each historic county also has its own preset map.
Trying it on two old favourites
Naturally I went straight for Pentre Ifan and Bryn Celli Ddu. Both turn up in all three datasets:
Pentre Ifan Chambered Tomb is scheduled as PE008, with a separate scheduling, PE504, for the standing stone 120 m SSW. It's also in the HER (Dyfed records such as DAT1471) and in Coflein as NPRN 101450.
Bryn Celli Ddu is AN002 to Cadw, GAT2694 in the HER and NPRN 93827 in Coflein. Around it sit a plough-levelled cairn, a cup-marked outcrop and an enclosure to the south-west. That's exactly the sort of landscape context I like to see.
One catch. The map viewer has no place-name or site-name search box that I could find. You either pan and zoom, or open the attribute table and filter it. If you know where you're going that's fine. A casual visitor typing "Pentre Ifan" will expect more.
Open data: better than it looks
This is where the geek in me cheered. The data layers sit on public ArcGIS Feature Services, so anyone with a GIS, a QGIS install or a few lines of code can query them directly. The site also says the open datasets from RCAHMW and Cadw can be downloaded from the platform. The NMRW layer carries a clear "Crown copyright: RCAHMW" credit, and the splash screen notes that copyright stays with each contributing body, whose terms apply. Records come in both Welsh and English. Cadw names have a Welsh form ("Beddrod Siambr Bryn Celli Ddu"), and the NMRW has Welsh fields too. There's also a Cymraeg button on the map and a separate Welsh-language hub.
No LiDAR here, though
As a LiDAR obsessive (I built LiDAR Lens for Wiltshire), I looked hard for a hillshade layer and didn't find one in this beta. Wales has good open LiDAR, and a hillshade under the HER points, with a swipe against the enclosure maps, would be a wonderful combination.
On the phone
It works on a phone. The tools sit along the top and the layer list slides up from the bottom. It's a bit cramped, though, and on a narrow screen the Cymraeg button sits over the toolbar. You also have to tick a terms box on every visit before the map will let you in. Both are fair beta niggles.
Verdict
It's an excellent idea: three national datasets, a quarter of a million HER points and a growing library of georeferenced historic maps, all in one free viewer with open services underneath. Add a search box and some LiDAR, and England would have a real reason to be jealous. The beta runs until 1 December 2026 and the team really does want comments, so if you have a Welsh corner you love, give it a try and use the Feedback button on the home page.

https://www.sarsen.org/2026/10/historic-wales-first-look-at-new-map.html

#historicwales #welshheritage #map #historicmapping #historicenvironment #nationallibrary #welshgovernment #look #rcahmw #monuments

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The Wiltshire Tornado of 1859: Thirteen Miles of Ruin At about ...

2026-10-19T22:47:24Z

The Wiltshire Tornado of 1859: Thirteen Miles of Ruin

At about half-past one on Friday 30 December 1859 a tornado crossed north Wiltshire from Bowood Park, near Calne, to Ogbourne St George. This page is the companion to the short film Thirteen miles of ruin, with the sources behind each card.
The survey
Alfred Charles Smith, rector of Yatesbury, walked the whole track and published his account in the Wiltshire Archaeological and Natural History Magazine the following year. His figures: the storm "shaped its course for E.N.E., and took nearly a straight line in that direction for about thirteen miles, its breadth varying from 250 to about 400 yards". It took two or three minutes to pass any one place. He declined to estimate its forward speed, and no one was killed.
Smith also gave the geometry of the track: "a line drawn from the point of its commencement, one mile south of Calne, to that of its final disappearance at Ogbourn St. George, will very nearly pass through every farm estate and village enumerated above". That line is 12.8 miles long at a true bearing of 76°. The film draws exactly that line, with the places he names plotted beside it at their modern village centres. The red band is a diagram of a 300-yard breadth, not a surveyed boundary.
Smith's line from Bowood to Ogbourne; the red band is a 300-yard diagram, not a surveyed track. Map data © OpenStreetMap contributors.
Along the track
Bowood Park: "where it broke off the large branch of an oak tree within the precincts of Bowood Park" — the first damage, about a mile south of Calne.
Quemerford: "astonishing the inmates by bursting in the door and windows".
Blackland: "swept down no less than one hundred and forty eight trees, some of great size and beauty".
Hail Farm (now Hayle Farm): "a vast number of trees (amounting in all to about one hundred) were prostrated in every direction".
Cherhill: "scarcely a tree stands unscathed … and scarcely a cottage retains its roof".
Yatesbury, Smith's own parish: "taking up a heavy broad-wheeled waggon weighing 22 cwt., and lifting it over a high hedge". 22 cwt is about 1.1 tons.
Winterbourne Monkton: "the old Rectory House, which had stood for many generations was altogether dismantled and became a ruin".
Hackpen Hill: "even to the summit of old Hackpen … merely giving a passing salute by scattering a little thatch here and there".
Temple Farm: "where it overturned several trees, and tore off the thatch of barns and other buildings".
Ogbourne St George: "where it left its last parting token, by blowing down a small barn and two trees".
Why a tornado
Most trees fell eastward, along the track. The telling exceptions are the trees that fell towards each other: in a triangular meadow west of Cherhill, the trees on both long sides fell inward, and west of Yatesbury churchyard two parallel rows fell across the track towards each other. A few trees fell with their heads to the west, against the gale: two at Quemerford, one at Cherhill, one at Yatesbury. Eastern roof slopes were stripped while the western faces, which took the wind, stayed on. Convergent falls, backward falls and lee-side unroofing are what a rotating vortex explains. George Rowell, who spent three days on the track, could not see a whirl and preferred a downrush of air behind falling rain; four backward trees are a thin sample.
Rowell's sketch map of Cherhill; the arrows show "the direction of the wind, as indicated by the fallen trees".
Hail
At Bowood, Mr Spenser saw hailstones "nearly half an inch in thickness, and from two to three inches in diameter, star-shaped, with rays ranging from four to seven in number". Others were wedge-shaped, about three inches long, and fell clear of the rain.
Rowell's plate of the hailstones.
The weather that day
The NOAA/CIRES/DOE 20th Century Reanalysis (version 3) rebuilds weather maps for 1859 from surface pressure observations. At noon on the 30th the low had moved away to the north and southern England lay in a strong south-westerly. The tornado cannot appear in it: the nearest grid point to Yatesbury is 49 km (30 miles) away, and the track was a few hundred yards wide.
At the Radcliffe Observatory, Oxford, the register for the 30th reads "Stormy", wind south-west, rain 0.37 inch, anemometer 569 miles in the day, about 24 mph. The barometer was rising: 29.133 inches on the 29th, 29.422 on the 30th. The register does not mention the tornado. (Rowell's lecture gives 25½ mph from the west-south-west.)
How strong?
TORRO's list rates the event T6, Calne to Ogbourne St George, ST9769 to SU2074 (Brown, Meaden & Rowe 2013). Read against the TORRO scale, Smith's descriptions — mature elms uprooted, roofs removed in one piece, a garden wall laid flat, a loaded waggon lifted — fall in the T4 range, perhaps T5 if the Winterbourne Monkton rectory walls failed rather than only its roof. That is a reading of the descriptions, not a damage survey.
Notes on the film
The track is Smith's stated line, not a route joined through village centres. Village points are modern centroids.
No forward speed is given, because Smith gave none.
Weather map: 20CRv3 ensemble mean, sea-level pressure every 4 mb, 10 m wind.
Music: original.
Sources
Smith, A. C. 1860. The Great Wiltshire Storm of December 30th, 1859. Wiltshire Archaeological and Natural History Magazine 6: 365–388.
Rowell, G. A. 1860. A Lecture on the Storm in Wiltshire. Oxford.
Burt, S. (ed.). Radcliffe Observatory, Oxford: meteorological observations 1853–1860. figshare, doi:10.6084/m9.figshare.13333925.
Slivinski, L. C. et al. 2019. Towards a more reliable historical reanalysis: improvements for version 3 of the Twentieth Century Reanalysis system. Quarterly Journal of the Royal Meteorological Society 145: 2876–2908.
Brown, P. R., Meaden, G. T. & Rowe, M. W. 2013. Tornadoes in Great Britain and Ireland to 1960: Part 3: years AD 1851–1875. International Journal of Meteorology 38 (378): 68–73.
Map data © OpenStreetMap contributors.

https://www.sarsen.org/2026/10/the-wiltshire-tornado-of-1859-thirteen.html

#thirteenmiles #wiltshiretornado #bowoodpark #ruin #wiltshirearchaeological #farm #calne #george #smith #ogbourne

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A Mystery Square in the Stonehenge Landscape Lidar Lens view ...

2026-10-17T08:34:32Z

A Mystery Square in the Stonehenge Landscape

Lidar Lens view
About 650 m north-north-east of Stonehenge, just north of the Avenue, there is a square. On the modern Environment Agency lidar it is very obvious: a ditched enclosure about 60 m across, centred at SU 1254 4278, with its sides running close to the grid. So what is it? I don't know, and that's rather the point of this post. It's a little mystery.
Who saw it first?
The first sign I know of was in 2010, when Simon Banton posted a relit image of the early lidar on his blog with a box over this spot marked "What's this then?" That post is no longer online, and I'm grateful to Simon for kindly supplying me with a copy.
Simon Banton's 2010 relit image of the early lidar, "What's this then?" Image: Simon Banton, used with thanks.
What it isn't
I can't see it for certain on any of the early aerial photographs. That's perhaps not surprising, as it had been a cultivated, ploughed field.
The Wiltshire & Swindon HER has a record nearby (MWI79347) for a feature seen on lidar, but that is described as a circle about 140 m across, with a bank. Different shape, different size, so it isn't this.
Nor is it the wartime pillbox that shows on the 1943 USAAF aerial photographs (Currently offline). That stood about 230 m to the west-north-west, at SU 12320 42854.
And it doesn't show on the geophysics. The 2011 magnetometer survey covers the square fully, and there is nothing there (Darvill et al. 2013, Fig. 4B).
So what is it?
Why hasn't it been spotted before, when it's so plain on the lidar now? That's an open question. My best guess, and it is only a guess, is that because it's square rather than round it is more likely to be something agricultural, a sheep pen or fold or something similar, than anything ancient. If you know better, I'd love to hear.
Acknowledgements
Thanks to Simon Banton for a copy of his 2010 blog post.
References
Banton, S. 2010. 'I love LIDAR and PTM', Novacaster Community blog, 4 Oct 2010 (no longer online; copy kindly supplied by Simon Banton).
Darvill, T., Lüth, F., Rassmann, K., Fischer, A. & Winkelmann, K. 2013. Stonehenge, Wiltshire, UK: high resolution geophysical surveys in the surrounding landscape, 2011. European Journal of Archaeology 16(1), 63–93. doi:10.1179/1461957112Y.0000000025
US 7th Photographic Group, 24 Dec 1943, sortie LOC122 frames 1022 and 1050
Wiltshire & Swindon HER, MWI79347.
Environment Agency LIDAR, Open Government Licence.

https://www.sarsen.org/2026/10/a-mystery-square-in-stonehenge-landscape.html

#stonehengelandscape #simonbanton #mysterysquare #lidar #agencylidar #environmentagency #darvill #thanks #avenue #open

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The Boles Barrow bluestone This post is the companion to the ...

2026-10-16T10:12:04Z

The Boles Barrow bluestone

This post is the companion to the short film The Boles Barrow bluestone: a 400 kg exotic in Salisbury Museum, the claim that it came from a long barrow older than Stonehenge, and why every link in that claim breaks.
An exotic, not an erratic
The stone at the British Museum, 2022 · T. Daw
The boulder is Preseli spotted dolerite (Thomas, in WAM 1924; Thorpe et al. 1991), now Salisbury Museum SBYWM:1934.68. On Salisbury Plain it is an exotic: a rock lying far from its geological source, however it got there. An erratic is an exotic moved by a natural agent, usually glacial ice; every erratic is an exotic, but not every exotic is an erratic. Whether this one is an erratic depends on how it reached the Plain, and the evidence for that is where it was first found: in a long barrow older than Stonehenge, or at Stonehenge itself.
Why it matters
Boles Barrow, Environment Agency LiDAR 1 m (2022), silver hillshade, low sun from the north-west · OGL v3.0
Boles (Bowls) Barrow, ST 94204 46771, is a long barrow 18.6 km west of Stonehenge. Five of its thirteen primary burials have been dated, the latest to 3760–3630 cal BC (Parker Pearson et al. 2015). Stonehenge's first bluestones were set up about 3000 BC. A bluestone buried in the barrow would put bluestone on the Plain centuries before Stonehenge, and since Thorpe et al. (1991) the stone has been cited as evidence that glaciers, not people, carried the bluestones east. In 2015 Parker Pearson and colleagues thought a Boles Barrow origin "highly probable"; in 2020 Parker Pearson and Richards concluded it "cannot be the Boles Barrow stone". The British Museum's 2022 label hedged: "Boles Barrow or Stonehenge".
The dig is in the archive
Colt Hoare, Ancient Wiltshire I (1812), Heytesbury Station III · photo T. Daw
William Cunnington opened the barrow in 1801. His letter to H. P. Wyndham of 18 July 1801, known from a copy in his daughter Elizabeth's hand, describes "a ridge of large stones and flints" over the burials; a footnote in his own hand gives their weight: "from about 28lbs. to 200 lbs." The letter calls them "of the same species of Stone as the very large Stones at Stonehenge … what the Country people call Sarsens". No bluestone is mentioned, and Colt Hoare's account (1812, pp. 87–88) has none either. The digs of 2023 and 2024 found no bluestone (The Past, 27 May 2023).
Too big
Salisbury Museum, 2012 · T. Daw
Wyndham, writing to Colt Hoare in 1802, described the same stones as "from 28lbs. to 200lbs. in weight", "similar in substance to many at Stonehenge and … often found peeping out from the turf or just under it, in the vallies of our downs like those near Abury". These are local sarsens of 13 to 91 kg. Published weights for the bluestone boulder run from 340 kg (Williams-Thorpe & Thorpe 1992) to 611.64 kg (Salisbury Museum label, 2012); the film says "around 400 kg".
An undated note
The only link is a second footnote in Cunnington's hand on the copy of the letter. As printed in 1924: "Since writing the above I discover among them the Blue hard Stone also, ye same to some of the upright Stones in ye inner Circle at Stonehenge." The first printing, in 1922, reads "I discovered amongst them the Blue hard Stone, ye same as the upright Stones in ye inner Circle at Stonehenge", and its editor, B. Howard Cunnington, thought it "possible that after the letter to Mr. Wyndham was sent, the foregoing note was added as a memorandum". A second copy of the letter carries the footnote mark but no note. The note gives no date and no size.
Matched in 1923
Salisbury Museum, 2016 · T. Daw
The boulder was connected to the note 122 years after the dig. In 1923 B. Howard Cunnington searched William Cunnington's old garden in Heytesbury and found three sarsens and a Dartmoor granite block, "but no 'Blue Stone'". Lord Heytesbury then found a bluestone under a beech tree at Heytesbury House. His aunt, the Hon. Mrs Hamersley, recalled that "the stone was removed from the late Mr. Wm. Cunnington's garden at Heytesbury to its present site at Heytesbury House before 1860. It was called the 'Stonehenge Stone'." On that account and Dr H. H. Thomas's identification of the rock, B. Howard Cunnington concluded that "there can be little doubt" it was the Boles Barrow stone, explaining its name as arising "from its similarity to the Blue Stones". An 1864 family letter records that another stone in the same garden had been wrongly "supposed … a stone brought from Stonehenge".
Where Colt Hoare did find bluestone
Colt Hoare (1812), p. 127
Colt Hoare did record bluestone when he found it. Amesbury No. 16, near Stonehenge, was "a mutilated flat barrow, 76 feet in diameter", a round barrow whose primary burial was a cremation in a cist with "a spear head of brass in fine preservation, and a pin of the same metal": a Bronze Age burial, later than Stonehenge. Over the cist "we found a large piece of one of the blue stones of STONEHENGE", which, he wrote, "decidedly proves that the adjoining temple was erected previous to the tumulus". On the same page he noted that the sarsen pieces in the barrow were "chipped off, (I am sorry to say) like those now daily knocked off from the great fallen trilithon".
(Boles Barrow) Stonehenge Bluestone 2016 by Adam-Stanford - ASGS on Sketchfab
Notes on the film
Every link between the boulder and Boles Barrow breaks: it was not recorded at the dig; it is several times heavier than the stones that were; the note that mentions a "Blue hard Stone" is undated and gives no size; and the boulder was matched to the note only in 1923, at another house, where it was known as the Stonehenge Stone. It is much more likely to have been obtained from Stonehenge, by whom and when is not known: it may have left the monument centuries before Cunnington, when stone was being taken from it. If so, it is no evidence for glacial transport of bluestones to Salisbury Plain. Accounts of its surface differ: "certainly has been dressed" (1924), "appears unworked" (1992), parts "worked down with metal tools" (Parker Pearson & Richards 2020). The note is quoted from its printed versions; the manuscript has not been re-examined. Photographs: T. Daw. Map: contains OS data © Crown copyright and database right 2026 (OS Terrain 50, Open Rivers, Open Names). LiDAR: contains Environment Agency data, © Environment Agency copyright and/or database right 2022, Open Government Licence v3.0. Music: original. Earlier posts: The Bowls Barrow Bluestone in Salisbury Museum (2012), The Bowls or Boles Barrow Bluestone – a Red Herring (2016), The Boles Barrow Bluestone (2022), Colt Hoare's description (2022), Did Cunnington find any bluestone in Boles Barrow? (2024).
Sources
British Museum 2022. The world of Stonehenge, exhibition label and large-print guide, p. 38.
Colt Hoare, R. 1812. The Ancient History of Wiltshire, vol. I, pp. 87–88, 127.
Cunnington, B. H. 1922. "Blue hard stone, ye same as at Stonehenge," found in Boles [Bowles] Barrow (Heytesbury, I.). Wiltshire Archaeological and Natural History Magazine 41, 172–174.
Cunnington, B. H. 1924. The "Blue Stone" from Boles Barrow. Wiltshire Archaeological and Natural History Magazine 42, 431–437.
Parker Pearson, M. et al. 2015. Antiquity 89.
Parker Pearson, M. and Richards, C. 2020. The Stonehenge bluestones. In M. Parker Pearson et al., Stonehenge for the Ancestors, Part 1. Leiden: Sidestone, p. 174. doi:10.59641/x8a4u5v6w7
The Past 2023. The latest from the past: Re-excavating Boles Barrow. 27 May. the-past.com
Thorpe, R. S. et al. 1991. Proceedings of the Prehistoric Society 57.
Williams-Thorpe, O. and Thorpe, R. S. 1992. Geochemistry, sources and transport of the Stonehenge bluestones. Proceedings of the British Academy 77, 133–161.

https://www.sarsen.org/2026/10/the-boles-barrow-bluestone.html

81 degrees at Stonehenge This post is the companion to the short ...

2026-10-16T09:34:27Z

81 degrees at Stonehenge

This post is the companion to the short film 81 degrees at Stonehenge. It sets out why two stones at the centre of the monument are turned off the solstice axis, how far, and how the angle can be laid out with a single straight line. The evidence, numbers and caveats follow.
The axis
Stonehenge's main axis runs from the midsummer sunrise in the north-east to the midwinter sunset in the south-west, through the entrance gap between Stones 30 and 1. The reference value used here is the geometrical axis of the trilithon horseshoe, 49.95° true (49.81° on the National Grid; Thom et al. 1974), which Ruggles takes as the best estimate (49.8° ± 0.2°). Most of the stones at the centre are set square to it. Two are not.
Plan of the standing stones with the solstice axis. Stone positions from T. Daw's 3D model; Stone 56 from the Rees 1989 survey.
The Altar Stone
Atkinson (1956) noted that the Altar Stone, the recumbent green sandstone slab at the centre, does not lie at right angles to the axis. Gordon and Phyllis Freeman (2001) observed that its twist lines it up with the midwinter sunrise. Simon Banton later ran the same line through a tooled notch in Stone 58 and along the edge of Stone 53, and found it ran along the centre line of the Altar Stone. Parker Pearson et al. (2024) describe its long sides as "aligned approximately on the midwinter sunrise".
Most of the Altar Stone lies under the fallen Stone 55 and lintel 156, so modern surveys show only small exposed patches. The two plans that draw its whole outline, Petrie's (1880) and Atkinson's plan of his cutting 53 (Cleal et al. 1995, Fig. 286), put its long axis at about 82–83° to the solstice axis, each to about ±1.5°. The film calls it "near 81°".
The Altar Stone against a square-set line. Outline schematic.
Stone 56 and the Great Trilithon
Stone 56, the tallest stone at Stonehenge and the surviving upright of the Great Trilithon, is turned the same way. The twist was first noted on sarsen.org in June 2012 and published in 2015 as "about 80°" to the axis, a skew of about 10° (Daw 2015). Stone 56 was leaning badly in 1901, and William Gowland excavated around it while it was straightened. His record shows it was reset in its original position, and his excavation of the socket of the fallen Stone 55 showed how its partner had stood:
"If set back in its place thus indicated the 'recumbent stone' would be exactly in line with the 'leaning stone.'" (Gowland 1901)
The recumbent stone is 55; the leaning stone is 56. The whole trilithon, not one stone, was set on the twisted line.
W. Gowland, "Plan of the excavations around the stone", Archaeologia 58 (1902), Fig. 7. Public domain.
Three surveys of Stone 56
Stone 56 is wedge-shaped at ground level. Its inner (north-east) face is rough and stands roughly square to the axis; its back (south-west) face is straight, and it is the back face that the midsummer sun sets along. The back face was measured on three independent surveys, each outline digitised and a straight line fitted to the middle 60–70% of the face:
Gowland's 1901 excavation plan (1902, Fig. 7), oriented by its drawn north arrow: 80.0–80.7°.
M. J. Rees & Co. for English Heritage, 1:200 on the National Grid, 1989: 82.0°.
The English Heritage laser scan of 2011 (Abbott & Anderson-Whymark 2012, Fig. 1): 80.1°.
The mean of the three is 80.8°, each figure good to about ±1–1.5°. Two further plans, not independent of these, give 80.5° (Cleal et al. 1995, Plan 2) and 81.4° (Field et al. 2015, Fig. 2). A stone set square to the axis would read 90°.
The three independent outlines of Stone 56 and their back-face lines. Gowland's outline is placed nominally on the Rees centroid; its angle is unaffected.
Stone 56 as surveyed in 1989, its back face extended, at 81° to the axis
Not just two stones
Other features at the centre follow the same twisted line (Daw 2015). Two postholes north-east of the Altar Stone, 3362 and 3364, mark a pair of wooden posts set on it. At the south-western end of the inner bluestone horseshoe, the pair of bluestone pillars 66 and 68 (68 now pushed over, its original position known from Gowland's records) define the end of the horseshoe on the same alignment. The outer bluestone circle, badly damaged near the axis and largely unexcavated, appears to be twisted the same way. None of these on its own proves the twist was deliberate; together they show it was not confined to one stone.
The sky in 2500 BC
The direction of sunrise at a solstice depends on the latitude and on the tilt of the earth's axis, which changes slowly. For Stonehenge (51.18° N) in 2500 BC, with the obliquity of the ecliptic at 23.973° (Vondrák et al. 2011), the midsummer sun rose at 49.6° and the midwinter sun at 130.4°, on a level horizon. The two sunrises were 80.8° apart. The same angle separates the two sunsets, and so the main axis (midsummer sunrise to midwinter sunset) and the second solstice line (midwinter sunrise to midsummer sunset) cross at 80.8°. A horizon altitude of 0.6° changes this by only 0.02°. The angle depends mainly on the date: it was 80.6° in 2000 BC and is 78.8° today. Simon Banton's figure for 2500 BC is 80° 49′ 25″.
The Altar Stone and Stone 56 lie along the second line. Seen from inside the circle, the midsummer sunset runs down the back face of Stone 56; it was photographed there in 2014, 2015 and 2022. The midwinter sunrise no longer reaches that direction, so Banton (2026) photographed the major-standstill moonrise of 2024–25 in its place, through the notch in Stone 58 and along the Altar Stone.
The four solstice directions at Stonehenge, 2500 BC. Diagram, level horizon.
Midsummer sunset beside Stone 56. Photo: T. Daw, 2015.
The clock face
The outer sarsen circle had 30 uprights and 30 gaps. Taking the centres of both gives sixty equally spaced marks round the circle, like the minutes on a watch (Daw 2024). Set the main axis from 12 (midsummer sunrise) to 6 (midwinter sunset). The entrance gap is at 12, so the stones fall on the odd minutes and the gaps on the even ones.
A straight line from the 15-minute mark to the 42-minute mark crosses the axis at exactly 81°. The geometry is simple: a chord between marks a and b is perpendicular to the radius through their midpoint, so it lies at 3(a + b) + 90 degrees to the axis, modulo 180. For 15 + 42 = 57, that is 81°. Any chord whose ends add to 57 is parallel to it.
The sixty-mark circle, the axis from 12 to 6, and the 15–42 line at 81°. The Altar Stone and Stone 56 are drawn parallel to the line: schematic.
The gaps matter. Chords between stone centres alone come out in steps of 6°, so the nearest to 81° are 78° (15 to 41) and 84° (15 to 43). Only with the gaps counted does 81° fall out. A sixty-mark circle can make any multiple of 3° with one chord, so 81° is easy to set out rather than forced by the circle; the case is that it is easy and it matches the sky.
Stones only: 78° and 84°. Stones and gaps: 81°.
The Bush Barrow lozenge
The gold lozenge from Bush Barrow (Wilsford G5), on Normanton Down about a kilometre south-west of Stonehenge, was dug by William Cunnington for Richard Colt Hoare in 1808 and is now in the Wiltshire Museum, Devizes. It is a sheet of gold 184 × 156 mm, from a burial of about 1950 BC, some five centuries after the sarsens went up. Thom, Ker and Burrows (1988) measured the acute angles of its diamond at 81° and noted that this was the angle between the midsummer and midwinter sunrises at the latitude of Stonehenge (MacKie 2009). The Wiltshire Museum's own page gives 80°.
The Bush Barrow gold lozenge, Wiltshire Museum, with its acute angle marked "about 81°" (the published figure; the photo is taken at an angle through display glass and is not a measurement). Photo: Pasicles, CC0, via Wikimedia Commons.
Caveats
The Altar Stone may once have stood. Atkinson (1956) and Cleal et al. (1995) left open that it was a fallen upright. Burl (2006) and Parker Pearson et al. (2024) favour a deliberate recumbent; Burl put the chance of a fallen upright landing on the solstice line at about 1 in 165. It is not settled by excavation.
Precision. Ruggles (1997) warns that Stonehenge's near horizon does not justify alignment claims finer than about 1°. The angle here is a ground layout, not a horizon sighting, and Stone 56's back face is measured to about ±1–1.5° on each survey. The Altar Stone is near 81°, not measured to a degree.
The lozenge is later. A shared angle on a craft object of c. 1950 BC is suggestive, not proof of shared knowledge.
Sixty marks is a circle, not a number system. There is no evidence of base-60 counting in Neolithic Britain. That the builders used the 15–42 chord is a hypothesis; the geometry and the sky angle are not.
Not the same as the calendar theory. Darvill (2022) proposed that the sarsens encode a solar calendar; Magli and Belmonte (2023) rejected it. The clock-face reading here is about angles, not days.
Notes on the film
The plan of the standing stones comes from T. Daw's 3D model of Stonehenge. The orientations of Stone 56 and the Altar Stone in that model were set from the Twisted Trilithon paper, so they are not used as evidence: Stone 56 is drawn from the Rees 1989 survey outline, and the Altar Stone is marked as schematic.
On the clock-face diagrams the Altar Stone and Stone 56 are placed at their plan positions and drawn parallel to the 81° line, as an illustration.
Sun positions are for 2500 BC on a level horizon, for the centre of the disc.
Sources
Abbott, M. and Anderson-Whymark, H. 2012. Stonehenge Laser Scan: Archaeological Analysis Report. English Heritage Research Report Series 32-2012.
Atkinson, R. J. C. 1956. Stonehenge. London: Hamish Hamilton.
Banton, S. 2026. The secondary solstice axis at Stonehenge: using the Moon as a proxy for the ancient Sun. Journal of Skyscape Archaeology, 133–141. doi:10.1558/jsa.33686
Burl, A. 2006. Stonehenge: A New History of the World's Greatest Stone Circle. London: Constable.
Cleal, R. M. J., Walker, K. E. and Montague, R. 1995. Stonehenge in its Landscape: Twentieth-century Excavations. English Heritage Archaeological Report 10.
Darvill, T. 2022. Keeping time at Stonehenge. Antiquity 96: 319–335. doi:10.15184/aqy.2022.5
Daw, T. 2015. The Twisted Trilithon of Stonehenge. Wiltshire Archaeological and Natural History Magazine 108: 15–24.
Daw, T. 2024. Sexagesimal Stonehenge: the geometry of the Stonehenge sarsen trilithons. doi:10.13140/RG.2.2.16275.86560
Daw, T. 2025. The geometry of the horseshoe stones at Stonehenge. doi:10.13140/RG.2.2.23505.65127
Field, D. et al. 2015. Analytical surveys of Stonehenge and its environs, 2009–2013: Part 2, the stones. Proceedings of the Prehistoric Society 81: 125–148. doi:10.1017/ppr.2015.2
Freeman, G. R. and Freeman, P. J. 2001. Observational archaeoastronomy at Stonehenge: winter solstice sun rise and set lines accurate to 0.2° in 4000 BP. In J.-L. Pilon, M. W. Kirby and C. Thériault (eds), A Collection of Papers Presented at the 33rd Annual Meeting of the Canadian Archaeological Association, 200–219.
Gowland, W. 1901. The recent excavations at Stonehenge, with inferences as to the origin, construction, and purpose of that monument. Abstract of a report presented to the Society of Antiquaries, 19 December 1901. Man.
Gowland, W. 1902. Recent excavations at Stonehenge. Archaeologia 58: 37–118. doi:10.1017/S0261340900008882
MacKie, E. W. 2009. The prehistoric solar calendar: an out-of-fashion idea revisited with new evidence. Time and Mind 2: 9–46. doi:10.2752/175169709X374263
Magli, G. and Belmonte, J. A. 2023. Archaeoastronomy and the alleged "Stonehenge calendar". Antiquity. doi:10.15184/aqy.2023.33
M. J. Rees & Co. 1989. Stonehenge survey, 1:200, drawing AS16/1, for English Heritage. Historic England Archive MP/STO0861.
Parker Pearson, M. et al. 2024. Stonehenge and its Altar Stone: the significance of distant stone sources. Archaeology International 27: 113–137. doi:10.14324/AI.27.1.13
Petrie, W. M. F. 1880. Stonehenge: Plans, Description, and Theories. London: Stanford.
Ruggles, C. 1997. Astronomy and Stonehenge. In B. Cunliffe and C. Renfrew (eds), Science and Stonehenge. Proceedings of the British Academy 92.
Thom, A. et al. 1974. Stonehenge. Journal for the History of Astronomy 5: 71–90.
Thom, A. S., Ker, J. M. D. and Burrows, T. R. 1988. The Bush Barrow gold lozenge: is it a solar and lunar calendar for Stonehenge? Antiquity 62: 492–502. doi:10.1017/S0003598X00074597
Vondrák, J., Capitaine, N. and Wallace, P. 2011. New precession expressions, valid for long time intervals. Astronomy & Astrophysics 534: A22.
Earlier posts on sarsen.org: Twisted Stone 56 (2012); The Twisted Trilithon of Stonehenge (2015); Sexagesimal Stonehenge (2024); Stonehenge clockface solstitial alignments (2025); Visualising the secondary solstice axis (2026).

https://www.sarsen.org/2026/10/81-degrees-at-stonehenge.html

LiDAR Lens for Wiltshire This post has a companion short film A ...

2026-10-16T08:55:27Z

LiDAR Lens for Wiltshire

This post has a companion short film A LiDAR lens for Wiltshire, which shows the Lens at work in two minutes: the sun turning over the field banks in Great Ridge Wood, six ways of drawing the same ground, Stonehenge, and What's here? on a barrow beside it.
Anyone who has walked Wiltshire for long knows the ground is full of lumps and dips that the aerial photographs don't explain. Crops, hedges and trees hide a great deal. LiDAR takes the vegetation away and leaves the bare earth, and the Environment Agency has kindly flown most of the country and made the results free. The snag has always been getting the best from it without a GIS degree and a lot of patience.
So I have built something to make it easier, and it is now open to anyone: the LiDAR Lens for Wiltshire. It is free, there is no login, and it works on a phone as well as a desktop.
What it does
It covers all of Wiltshire and Swindon, about 3,800 km², using the Environment Agency's 1 m LiDAR composite terrain model laid over Esri aerial imagery, with OpenTopoMap as a background map.
The idea is simple. A circular lens sits on the aerial photo, and you drag it about and resize it to see the bare ground underneath. Inside the lens you can choose how the ground is drawn:
hillshade, lit from a single direction or from several
slope
local relief model
sky-view factor
red relief
There are controls for sun angle, vertical exaggeration and colour, so you can tease out the faint stuff. Low sun, a bit of exaggeration and a slow sweep across a field is surprisingly addictive.
What’s here?
Click a spot and the "What’s here?" panel gives you plain measurements: local relief, size, elongation and edge slope. It also lists nearby recorded sites from Historic England's open data (scheduled monuments, listed buildings and aerial investigation mapping) and from OpenStreetMap, with links to the records.
Other bits
Historic OS maps from the National Library of Scotland (25-inch, six-inch and one-inch, roughly 1880s to 1920s) as overlays, handy for comparing old field boundaries and tracks with the ground today
Wiltshire Council public rights of way
Go to a grid reference, place name or postcode, or "Use my location" when you're out in the field
An elevation profile, share links, keyboard shortcuts and a help panel
Please use it responsibly
The public version contains no county Historic Environment Record data but a link to where the data can be obtained from is provided, observing uncertain copyright restrictions. Please respect landowners and stick to rights of way. Never dig or metal-detect on sites; scheduled monuments are protected by law. If you think you have found something new, report it to the Wiltshire HER at archaeology@wiltshire.gov.uk. They would much rather hear about it than have it dug.
Other counties welcome
There is nothing special about Wiltshire here, apart from it being the best county. The code is on GitHub under the MIT licence, and PROTOCOL.md walks through, step by step, how to build the same thing for your own patch. If you fork it for another county, do let me know.
I built it with a good deal of help from Grok Bot, and it is hosted on Cloudflare. It will have bugs and rough edges, so please leave a comment below with feedback, ideas, or anything interesting you spot.
Credits
LiDAR: Environment Agency, Open Government Licence
Aerial imagery: Esri
Recorded sites: Historic England, Open Government Licence
Historic maps: National Library of Scotland, CC-BY. Reproduced with the permission of the National Library of Scotland
Public rights of way: Wiltshire Council, Open Government Licence; contains OS data. This is not the legal Definitive Map
Map data © OpenStreetMap contributors
Background map: OpenTopoMap, CC-BY-SA
Notes on the film
Every shot is a screen capture of the public LiDAR Lens, made frame by frame with the viewer's own controls, so what the film shows is what the site shows. Places: Great Ridge Wood (field banks under the trees), West Woods near Lockeridge, Stonehenge, and the disc barrow 220 m south-west of Stonehenge (NHLE 1012385). The background throughout is the National Library of Scotland's six-inch Ordnance Survey map (one-inch for the county view), reproduced with the permission of the National Library of Scotland (CC-BY). LiDAR: Environment Agency LIDAR Composite DTM 1 m (OGL). Music: original.

https://www.sarsen.org/2026/10/lidar-lens-for-wiltshire.html

Stonehenge Aerodrome in 1919: a 3D model from the US National ...

2026-10-16T08:16:52Z

Stonehenge Aerodrome in 1919: a 3D model from the US National Archives photographs

Between 1917 and 1921 Stonehenge had an aerodrome for a neighbour, just to the west of the stones on either side of what is now the A303. Almost nothing of it survives on the ground, so I have built a 3D model of its buildings as they stood in early 1919. You can walk round it in your browser here:
Stonehenge Aerodrome, 1919: 3D model
The photographs
The starting point was a set of photographs taken on 20 February 1919 by Lt Sintzenich of the US Army Signal Corps, now held by the US National Archives (NARA). Each one is linked from the model, and here they are:
111-SC-153264: “View, looking east, showing a block of six hangars”, taken from the landing ground, with a biplane in an open shed.
111-SC-153265: “General view of landing field, with the Night Bombing School in the background”.
111-SC-153266: “View of hangars looking west”.
111-SC-153267, 111-SC-153268 and 111-SC-153269: three frames of the “Panorama of Stonehenge Camp, looking from southeast to southwest”.
111-SC-153276: a vertical view catalogued as the Night Bombing School. That was the other camp, by Fargo Wood, so its buildings are not laid out in this model.
How it was put together
Photographs alone don't tell you where things were, so the layout comes from maps. I traced 41 buildings from the Ordnance Survey six-inch map, Wiltshire LIV.SW, revised 1923, from the National Library of Scotland, and georeferenced it to the National Grid. Anything put up and taken down before 1923 may well be missing.
The big General Service sheds (the hangars) were set out from the RAF vertical photograph of 24 May 1921, reproduced in Martyn Barber's report Stonehenge Aerodrome and the Stonehenge Landscape (Historic England, 2014). It shows three coupled pairs of sheds end to end, with their ridges running north-east to south-west and the doors on the south-west gable ends. The north-easternmost pair, which I've called D, had gone by 1923, so it isn't on the OS map.
For the photographs, I worked back from the bearings of landmarks in each picture (hangar gables, a mast, huts, distant woods) to find where the camera must have stood. Several were taken from the roof of hangar pair B: the field views from its west corner and the camp panorama from its south corner. Photograph 264 was taken from the ground, out on the landing ground south-west of the row.
Using the model
Photo pegs: the yellow pegs mark where each photograph was taken. Click one (or the numbered buttons) to see the photograph and stand where the photographer stood.
Click a building to see its name and where the evidence for it comes from.
Compass: bottom right, so you don't lose your bearings.
Plan view with the 1923 map: open the plan with the OS overlay to check the model against the map.
Shed doors: this view looks into the open shed of pair A, where a little biplane sits, as in photograph 264.
Drag to look around, use the wheel to zoom and right-drag to move.
Credits and corrections
Photographs: Lt Sintzenich, US Army Signal Corps, 1919, US National Archives, public domain. Map: OS six-inch Wiltshire LIV.SW (revised 1923), reproduced with the permission of the National Library of Scotland, CC-BY. Hangar layout from Martyn Barber's 2014 Historic England report. Model by Tim Daw.
This is my best reading of the evidence, and I'm sure there are mistakes. If you know the site, the photographs or the aerodrome's history, and something looks wrong, please tell me in the comments. I'll happily fix it.

https://www.sarsen.org/2026/10/stonehenge-aerodrome-in-1919-3d-model.html

The Mystery of the Shrinking Barrows Lidar investigations Over ...

2026-10-16T07:34:57Z

The Mystery of the Shrinking Barrows

Lidar investigations
Over twenty years, the round barrows on land returned to grass around Stonehenge, much of it National Trust land, appear to have lost height. The average loss is 5 cm, about two inches, and the worst is more than a hand's width. Barrows in neighbouring fields whose use never changed have not moved. Either something is wearing down scheduled monuments in one of the most closely protected landscapes in Britain, or the lidar is being fooled. This post is the investigation.
The LiDAR differences and features can be explored at
https://lidar-lens-public.tim-daw.workers.dev/stonehenge-change/
How it started
Since 2000 most of the arable land in the Stonehenge part of the World Heritage Site has gone back to grass. The National Trust stopped arable farming on its holding that year, and by 2019 more than 526 ha was in permanent pasture (National Trust; National Trust 2019). Map 3 of the 2009 WHS Management Plan dates the reversions field by field from 2000 to 2011. Map 4 of the 2015 plan adds further fields reverted by 2015, without dates (WHS Management Plan 2015).
Two Environment Agency lidar surveys bracket the change. The first was flown on 8 December 2001 (survey P_2053, 1 m last-return DTM), while much of the land was still under the plough. The second is the National LIDAR Programme survey of 4 April 2021. The aim was modest: to see whether faint earthworks had begun to reappear once ploughing stopped. They had not. A search of the reverted ground found five patches of new relief, and all of them are modern, the largest being the turning circle for the visitor buses at SU 1207 4236. The barrows, however, did something else.
The oddity
Each mound was measured the same way in both surveys: a plane fitted to the ground beyond the mound was subtracted, leaving the mound's height above its surroundings. Seven mounds in fields reverted between 2003 and 2007 were on average 0.06 m lower in 2021. Eight mounds in grass since before 2000 had not changed, and nor had 27 that were still arable in 2008. The worst cases were a group of three bowl barrows (NHLE 1009620, −0.15 m), the 2 m bowl barrow north of Springbottom Farm (1009625, −0.11 m) and the long barrow north of Normanton Gorse (1008953, −0.06 m).
Figure 1. Normanton Down, reverted to grass 2003–2007. Left: December 2001. Centre: April 2021. Right: change in local relief, 2021 minus 2001; red = relatively lower now. 1 m grid, σ = 1 m smoothing, hillshade from the NW at 35°.
Figure 2. The control: Old King Barrows and the Avenue, grassland by 2000. Same processing and scale as Figure 1. No systematic change.
A few centimetres is well inside the ±15 cm absolute accuracy quoted for the older Environment Agency surveys, and close to the 0.10 m scatter of a single featureless test point. Before asking what happened to the barrows, the first job was to establish that anything had happened at all.
Ruling out the instrument
Levels. The whole 2021 surface sits higher than the 2001 surface: the median difference on tarmac roads in tile SU1040 is +0.083 m (n = 8,008). Each tile was levelled to its own road offset. Horizontal misregistration is under 0.5 m.
Stripes. The levelled difference map (Figure 3) shows north–south bands with a dominant east–west period of 417 m, the fingerprint of mismatched 2001 flight strips, plus 5–10 cm steps at field boundaries. The 2001 files contain no strip outlines, so the bands were removed empirically. Within each 1 km block of northing, the median difference was taken down each column of stable ground, smoothed over 51 m and subtracted. The correction spans −0.17 to +0.15 m (1st–99th percentile). Stable ground was defined in two ways, long-term grass only and all open fields, to check whether the choice drives the result.
Figure 3. Co-registered difference, 2021 minus 2001, tiles SU1040 and SU1035, 5 m smoothing, ±0.10 m; red = higher in 2021, blue = lower. North–south flight-strip banding and field-shaped steps dominate; woodland and built areas saturate.
Neighbours. Each mound top was compared with a ring of ground 10–30 m beyond its foot, in the same field and within 25 m of the mound in easting, so that any leftover striping affects mound and ring alike.
Decoys. Random points away from monuments, measured the same way, show no change in the reverted fields: −0.002 m (n = 58) and −0.004 m (n = 26).
More barrows. Adding OpenStreetMap tumuli to the scheduled monuments gives 157 measurable mounds in classed fields. After destriping and pairing:
Field history
n
Mound minus ring, mean change (m)
Lower / higher
p
Grass by 200058+0.00723 / 350.15
Reverted 2000–2011 (dated)47−0.05538 / 90.00003
Reverted 2008–2015 (undated)10−0.0077 / 30.34
Arable throughout400.00018 / 220.64
Two-sided binomial sign test. Long-term grass used as stable ground; using all open fields gives the same −0.055 m (38 / 9) and shifts no other class by more than 0.003 m.
The loss survives every step almost unchanged, and the control classes stay flat. Something real distinguishes the barrows in the early reversions. The later, undated reversions show nothing.
A second site. The best independent coverage is around Avebury, with a 0.5 m survey of May 2006 and National LIDAR Programme cover from winter 2018–19. Only three measurable mounds there lie in fields mapped as reverted, and those reversions are undated. All three are lower, by 0.024 m on average (p = 0.25), which is consistent with Stonehenge but not evidence. Cranborne Chase, the South Downs and the RSPB's Winterbourne Downs offered no field-located reversion, dated after an early survey, with enough mounds to test. Winterbourne Downs began reverting in 2006, after an October 2005 survey (Farm Wildlife 2020), but holds only four barrow listings.
The suspects
Sheep, rabbits and weather. Soil worn from the mounds should end up in the ring ditches. It has not: ring ditches in the 2000–2011 reversions are, if anything, 0.016 m deeper (n = 13, p = 0.58).
Settling fill. On the analogy of a Victorian well, loose ditch fill might compact and sink under grass. There is no sign of this at 1 m resolution, in ring ditches or in 188 transects across linear ditches (+0.006 m, p = 0.94).
Slumping plough soil. Soil heaped at barrow margins by ploughing would drop at the edge, not the top. The loss is greatest at the centre: −0.075 m within half the radius, against −0.024 m at 10–30 m.
Visible vegetation in 2001. The 2001 last-return surface sits about 6 cm above the DTM on mound tops, but equally on grassland mounds that did not shrink and on reverted ones that did. In the reverted classes it does not predict the size of the loss (r = −0.10, p = 0.51), and nor does 2001 ground roughness (r = −0.06, p = 0.68).
The 2001 processing. The striping shows that the 2001 processing left systematic errors, and the metadata name neither the sensor nor the ground filter. The neighbour comparison cancels anything that varies over tens of metres, but not an error that depends on surface type.
Grazing. In December 2001 many of these barrows were uncultivated islands in arable fields. Since reversion the National Trust has run "a tightly managed grazing regime", with many barrows mown or strimmed (National Trust). Island mounds that went to grass lost 0.044 m relative to their surroundings (34 down / 12 up, p = 0.002). Island mounds that stayed in arable did not (+0.005 m). No per-field grazing dates have been found.
The theory
The measurement compares a mound with the ground around it, and only in the early reversions did that contrast change between the flights. In December 2001 the mound carried rough, ungrazed grass and the ground around it was cultivated soil. By April 2021 both were short sward. A mat of dead grass and litter on an ungrazed island would hold the lidar ground surface a few centimetres above the soil on the mound but not on the field around it. The 2001 DSM-minus-DTM test cannot detect such a mat, because the last return and the filtered ground both land on top of it. Grassland mounds (grass all round at both dates) and arable mounds (the same island contrast at both dates) cancel out. Only mounds whose surroundings changed character should change, and that is what the table shows. On this reading the barrows have not shrunk at all. What has gone is the thatch.
Two pieces of evidence point the same way. On Normanton Down (Figure 1) the loss forms halos that enclose groups of mounds along the line of the former uncultivated strips, rather than circles round each mound. In 2021 the point cloud classes fewer returns as vegetation on these mound tops (3.3%) than on long-term grassland mounds (10.5%).
A witness
The barrows in Fargo Plantation, just south of the Cursus, are an independent test outside the reversions. In April 2009 the trees there still prevented a full earthwork survey (Bishop & Amadio 2010). Between the flights the plantation was thinned but left standing, and the vegetation was cleared from the barrows alone, a clearance I witnessed. Every one of those barrows is lower in 2021. Vegetation was removed from the mounds and not from their surroundings, and the lidar records it as lost height.
Loose ends
The later reversions show no loss, possibly because their mostly low mounds were ploughed over rather than kept as islands, or because some of that ground was still cultivated close to 2021: one field mapped as reverted by 2015 carries tramlines 20–25 m apart in 2021. The 13 named barrows of the Normanton Down group lose 0.034 m on average but split only 7 down / 6 up. In a small subsample, mounds reverted in 2007 lost more (−0.106 m, n = 3) than those reverted in 2003 (−0.025 m, n = 3).
Something else in the difference map
The same map holds a second, unrelated signal. West of Stonehenge, the field between the former A344 and the A303 is lower overall in 2021, but narrow strips within it have not changed (Figure 4). They run westward from the stones for a considerable distance, opening into a V, along the lines of former tracks to the monument. Ground compacted by long use as a trackway would settle less than the loosened plough soil around it. The old routes to the stones are recorded in how the ground has settled.
Figure 4. Co-registered difference, 2021 minus 2001, west of Stonehenge; red = higher in 2021, blue = lower, ±0.10 m. Pale east–west strips within the lowered field between the former A344 and the A303 mark ground that has not changed.
The verdict, for now
The signal is real and repeatable. Barrows in fields reverted between 2000 and 2011 measure about 5 cm lower relative to their surroundings in 2021 than in 2001, while barrows in long-term grass and long-term arable do not. The most economical explanation is that the barrows are intact. On the uncultivated islands, the surface the laser took for ground in 2001 lay above the soil, and grazing and clearance have since removed it. This is not yet proven, and an error in the 2001 processing that depends on surface type has not been excluded. Four checks would close the case:
Sensor and ground-filter details for the December 2001 flight from the Environment Agency, and from Bewley, Crutchley & Shell (2005), who describe the early lidar survey of the WHS.
Aerial photographs from 2000–2003, to map the uncultivated islands and test whether the loss stops at their edges.
Per-field grazing and mowing histories from the National Trust, the RSPB and Natural England.
A probe measurement of thatch depth on an ungrazed barrow and a grazed one nearby, the cheapest test of the missing 5 cm.
Methods
Environment Agency DTM, 8 December 2001 (P_2053, 1 m), and National LIDAR Programme DTM, 4 April 2021 (1 m), on a common grid with Gaussian smoothing (σ = 1 m). Mound centres were refined on the 2021 survey. A plane fitted beyond radius + 8 m was removed, and values were taken from azimuthally averaged radial profiles. Field histories come from the hand-georeferenced plan maps (15–50 m accuracy). Outside the WHS, Priority Habitat Inventory and CROME 2020–21 were used. Monuments are NHLE scheduled monuments plus OpenStreetMap tumuli.
References and data
Bewley, R.H., Crutchley, S.P. & Shell, C.A. 2005. New light on an ancient landscape: lidar survey in the Stonehenge World Heritage Site. Antiquity 79(305), 636–647. doi:10.1017/S0003598X00114577
Bishop, S. & Amadio, L. 2010. Stonehenge World Heritage Site Landscape Project: The Cursus Barrows and Surrounding Area. English Heritage Research Department Report Series 85-2010. Historic England
Stonehenge and Avebury WHS Steering Committees 2015. Stonehenge, Avebury and Associated Sites World Heritage Site Management Plan 2015. PDF
National Trust. Our work at the Stonehenge Landscape. nationaltrust.org.uk
National Trust 2019. Written Representation, A303 Amesbury to Berwick Down (TR010025). PDF
Farm Wildlife 2020. Case study: reversion of arable land to lowland chalk grassland. farmwildlife.info
Environment Agency / Defra lidar. Defra Data Services Platform; LIDAR DTM Time Stamped Extents
Historic England, NHLE scheduled monuments. Data downloads
Natural England Open Data (Priority Habitat Inventory); RPA Crop Map of England. naturalengland-defra.opendata.arcgis.com
OpenStreetMap contributors (ODbL), via the Overpass API.

https://www.sarsen.org/2026/10/the-mystery-of-shrinking-barrows.html

The Luftwaffe's Wiltshire Aerial Photos German reconnaissance ...

2026-10-16T06:05:43Z

The Luftwaffe's Wiltshire Aerial Photos

German reconnaissance aircraft photographed Wiltshire repeatedly between August and December 1940, and once more in August 1942. The prints and the Luftwaffe's target dossiers were captured in 1945 and are now in the US National Archives, scanned and free to use. This post explains what survives and how to read it. An interactive map plots every Wiltshire frame and dossier, with a link to each scan.
CLICK HERE to open the map: Luftwaffe's Wiltshire
Avebury - an example photo: click it to expand
Avebury henge (top centre) and Silbury Hill (left, beside the A4), 4 September 1940. GX 10004 SG, R, exposure 95, scale about 1:26,000. The titling strip reads GB 1060 R 4.9.40. NARA RG 373, NAID 220881704.
Where the photographs come from
The US National Archives (NARA) holds about 1.2 million Luftwaffe aerial photographs in a series titled German Flown Aerial Photographs, 1939–1945, part of Record Group 373. They are known as GX prints, from the GX numbers that identify each box. The captured material was duplicated and shared between Britain and the United States, and the British holdings are now in the National Collection of Aerial Photography (NCAP) in Edinburgh.
Allied teams found caches of German photographs, maps and target dossiers across Europe in 1945. The material was flown to the Allied Central Interpretation Unit at RAF Medmenham in June 1945 and sorted there until 1949. It later passed to RAF Brampton and, after declassification in the early 1990s, to Keele University. In 2008 it was transferred to what is now Historic Environment Scotland, as part of NCAP. NARA and NCAP have since worked together to scan the prints, and the scans appear in NARA's online catalogue.
A GX citation names the box, the camera and the exposure: GX 10004 SG, R, Exposure 95. NARA describes SG, SK and SD as camera position identifiers. The L, R and S letters within a sortie are not explained in NARA's guidance. In the Wiltshire prints, L and R frames at the same scale run in parallel lines, and S frames are at a smaller scale.
Wiltshire: 129 frames from ten sorties
A search of the NARA catalogue for Wiltshire in the German Flown Aerial Photographs series returns 129 frames. Every one is digitised and listed as unrestricted for use. NARA gives each frame a centre point and the nearest named place in its gazetteer, and the map plots those centres.
DateBoxFramesScaleCoverage (NARA place names)
17 Aug 1940GX 1009611:57,000Buttermere
18 Aug 1940GX 10134101:15,200; 1:38,000Grimstead, Whiteparish, Landford, Redlynch; Devil's Ditch, Bulford
18 Aug 1940GX 10135381:23,500; 1:76,000; obliquesMere and the Knoyles, the Wylye valley, Winterbourne Stoke, Normanton and Lake, Salisbury, Downton
4 Sep 1940GX 10004151:26,000; one obliquePurton and Leigh south through Clyffe Pypard, Avebury and the Vale of Pewsey to Bulford and Downton
29 Oct 1940GX 1023881:15,000Winterslow, West Dean, Whiteparish, Landford
29 Nov 1940GX 10484441:20,500; 1:52,000Winsley and Bradford-on-Avon east along the scarp to West Lavington, across the Plain to Amesbury, then to Clarendon and Redlynch
5 Dec 1940GX 1204811:8,500Bradford-on-Avon
11 Dec 1940GX 1196171:10,000Box, Kingsdown, Monkton Farleigh, Colerne, Biddestone, Malmesbury
15 Dec 1940GX 1193511:15,000Yatesbury Field, Cherhill
28 Aug 1942GX 120604obliquesWhiteparish, Landford, Redlynch
Two sorties crossed the county on 18 August 1940, the day of the large raids on RAF airfields later called the Hardest Day. GX 10135 alone produced 38 Wiltshire frames, running from Mere across the Wylye valley and the Stonehenge landscape to Salisbury.
The place name in each catalogue entry is the nearest gazetteer entry to the frame centre, not a description of the subject. Exposure 95 of GX 10004 is catalogued at West Kennett Long Barrow. The print shows Avebury henge, with the village inside its bank, and Silbury Hill beside the Bath road. A later hand has written on the back, in English, Avebury Stone Circle – Silbury Hill.
Reverse of the same print. NARA RG 373, NAID 220881704.
The target dossiers
A second NARA series, Target Dossiers Pertaining to the British Isles, 1938–1945 (Record Group 242, records seized from Germany), holds the Luftwaffe's target files. Thirty-six digitised dossiers cover twenty-nine places in Wiltshire, dated 1939 to 1942. A dossier is a set of sheets, usually three:
an annotated vertical photograph with the target outlined in red, a scale bar, the coordinates and height, and the date of the information (Stand);
an extract from a 1:50,000 map with the target outlined;
a printed target card, the Zielstammkarte, filled in by typewriter.
The Alton Barnes dossier (GB 10 391) is typical. The photograph sheet, marked N.f.D. (nur für den Dienstgebrauch, for official use only), outlines an airfield of 1,000 × 850 m. It notes probable administration and accommodation buildings and is dated October 1940. The map sheet is dated November 1940 and carries the stamp of Luftflotte 3 (Lfl. Kdo. 3).
Target sheet GB 10 391 b c, Alton Barnes, Flugplatz, Stand X.40. NARA RG 242, NAID 240794047.
Click to embiggen
The target card records, among other entries:
Location: 12 km SW of Marlborough; 1° 51′ W, 51° 21′ 30″ N; 136 m above sea level.
Target: Flugplatz (airfield), compared with the army camps at Marlborough, Chisledon, Yatesbury and Devizes by their own target numbers.
Significance: Als E-Hafen geeignet, suitable as an Einsatzhafen or operational airfield.
Description: Woodborough station 3 km S; landing ground about 850 × 1000 m; a few smaller buildings, probably quarters, in the south-east corner.
Recognition points: the Kennet and Avon Canal along the southern edge; the railway fork of the Newbury–Bath and Newbury–Warminster lines 5.5 km SW.
Neighbouring airfields: eleven, each with its target number, distance and bearing, from Boscombe Down (GB 10 22, 23 km SSO) to Marlborough (GB 10 887, 9 km NO); O is Ost, east. A red typed addition adds Clyffe Pypard, 14 km NNW, as an Einsatzhafen.
Information as of: November 1940.
Zielstammkarte (L) for Alton Barnes, Bearbeitungsstand November 1940. NARA RG 242, NAID 240794047.
What the Luftwaffe listed
Each target number begins with a country code and a category. The Wiltshire dossiers fall into four categories, and the type names below are the ones printed on the sheets:
CodeCategoryWiltshire dossiers
GB 10Airfields (Flugplatz)Alton Barnes, Boscombe Down, Clyffe Pypard, Colerne, Durrington, High Post, Larkhill, Lyneham, Marlborough, Netheravon, Old Sarum, South Marston, Tilshead, Upavon, West Overton, Wroughton, Yatesbury, Zeals
GB 14Army camps (Truppenlager, troop camp; Barackenlager, hutted camp; Zeltlager, tent camp)Bulford, Chisledon, Corsham, Devizes, Durrington, Heytesbury, Marlborough, Melksham, North Tidworth, Porton, Tilshead, Warminster, Yatesbury
GB 20Air force supply and depots (Luftpark, Nachschublager)Colerne, Hullavington, Lyneham, Wroughton
GB 22Ammunition depot (Munitionslager)Chilmark
Some sheets date their photographs. The Colerne airfield sheet cites a photograph of 30 November 1940, the Zeals sheet one of 21 November 1940, and the Tilshead camp sheet one of 13 December 1940. None of those dates matches a sortie in the Wiltshire photograph list, so the dossiers drew on cover beyond what is catalogued here. The Tilshead and Zeals sheets were reissued in a later, plainer format dated 1941 and 1942.
Catalogue notes
Searching the NARA catalogue by county misses some Wiltshire dossiers, and a few entries need correcting:
Colerne (GB 10 866 and GB 20 43) is catalogued under Gloucestershire.
South Marston (GB 10 373) is catalogued under "Berwicksire".
North Tidworth (GB 14 51) is catalogued under Hampshire.
Zeals is catalogued under Wiltshire, but its file unit places it in Somerset.
Boscombe Down has the local identifier GB 10-21. The sheets, the scan file names and the Alton Barnes card all give GB 10 22.
The Wroughton airfield dossier (GB 10 867, 27 scans) sits under the file unit for Dumfries.
Chippenham has a file unit in the series but no digitised dossier.
The photograph search covered frames whose catalogue entry names Wiltshire. Frames catalogued under a neighbouring county are not on the map.
Using the map
Photographs are coloured by sortie, in shades of pink from pale (August 1940) to deep (December 1940). Open rings are oblique views. Gold squares are dossiers, lettered by category: A for airfields, C for army camps, S for supply and depots, M for the ammunition depot. Click any point for the record, a preview of the scan and links to the full-size images. The key can switch sorties and categories on and off.
Photograph positions are NARA's frame centres, not footprints. Dossier positions are the coordinates printed on the sheets, to the nearest minute (about ±1 km). Where the sheet could not be read, the position is the station or camp itself.
Sources
National Archives and Records Administration. German Flown Aerial Photographs, 1939–1945. Record Group 373, Records of the Defense Intelligence Agency, series NAID 306065. catalog.archives.gov/id/306065
National Archives and Records Administration. Target Dossiers Pertaining to the British Isles, 1938–1945. Record Group 242, National Archives Collection of Foreign Records Seized, series NAID 3371016. catalog.archives.gov/id/3371016
GX 10004 SG, R, Exposure 95, 4 September 1940. NAID 220881704. catalog.archives.gov/id/220881704
Target Dossier for Alton Barnes, Wiltshire, England, GB 10-391. NAID 240794047. catalog.archives.gov/id/240794047
National Archives and Records Administration. RG 373 GX Foreign Aerial Photography (research guide). archives.gov
National Archives and Records Administration, The Unwritten Record (2019). Researching Foreign Aerial Photography: Captured German Aerial Prints. unwritten-record.blogs.archives.gov
National Collection of Aerial Photography. German Air Force (GX) collection. ncap.org/image-collection/gx
Luftwaffedata Wiki. Target Codes. luftwaffedata.co.uk
All images: NARA, listed as Use: Unrestricted. The map uses NARA catalogue data; basemaps © OpenStreetMap contributors, CARTO, Esri and OpenTopoMap.

https://www.sarsen.org/2026/10/the-luftwaffes-wiltshire.html

The Flight of GX 10484 On 29 November 1940 a German ...

2026-10-16T05:22:30Z

The Flight of GX 10484

On 29 November 1940 a German reconnaissance aircraft crossed Wiltshire from the Avon gorge to the Hampshire border with two cameras running. Its 44 Wiltshire photographs survive in the US National Archives. Joined in order, the long-lens frames make a strip some 40 km long, and the film below flies it again: Avoncliff, Trowbridge, Bratton, Salisbury Plain, Stonehenge, Amesbury, Redlynch. For where these prints come from and every other Luftwaffe frame of the county, see The Luftwaffe's Wiltshire and its map.
Two flights, one page of links. This post is the flight of 29 November 1940, Avoncliff to Redlynch.
For the flight of 18 August 1940, down the A303 to Stonehenge and Salisbury in high summer, see
The Flight of GX 10135.
Sortie GB 1209
NARA files the prints as box GX 10484. Each print carries its own record. A titling strip gives the German sortie number, the camera and the date: GB 1209 L 29 11 40. A data panel gives the film number, the exposure number and the focal length of the lens. In the bottom corners are a clock and a level bubble.
Two cameras ran together. The L camera had a lens of 505.13 mm and took the close views, about 4.6 km square on the ground (exposures 109–135, film 1537). The S camera had a lens of 200.56 mm and took views about 11 km square (exposures 84–103, film 955), mounted the other way round. The two scales differ by 2.5, the ratio of the two lenses, so both cameras were looking down from the same height.
The backs show the paper and the custody. Each is printed on Agfa-Lupex paper, annotated in German pencil, typed "GX 10484" and stamped "Copied by Photo Rec. & Serv's Div, AAG, Hq. USAF". Exposure 131 of the L run and exposures 91 and 96 of the S run are not in the NARA set. The whole sortie runs to 254 frames, beginning off the Devon coast; the Wiltshire stretch is this post's subject.
A picture every fifteen seconds
The clock in the corner of each print shows the time of exposure. The centre of the dial is covered by a pencilled "29.11. L", but the ends of the hands are clear. The hour hand stands just short of two throughout. The minute hand reads 34.3 on exposure 109 and 40.7 on exposure 135: 26 exposures in about 6½ minutes, roughly one every 15 seconds. Each reading is good to about ±0.2 minute.
The S camera's clock runs 2.2–2.5 minutes ahead of the L camera's over the same ground, so the two clocks were not set together. Neither the time zone nor morning or afternoon is written on the prints; the film gives the clock readings and no more.
Joining the frames
Each L frame overlaps the one before by about 55%, and each is about 2.1 km further on. The frames were matched on several thousand common points per pair, each against its neighbour and the one beyond, and fitted together in a single adjustment that holds the scale steady from end to end. Most joins fit to within 2–4 m on the ground; over the Avon gorge, where the valley sides shift between viewpoints, to about 8 m. Each part of the strip comes from one photograph only, with a narrow seam between frames, so that hedges and trees are never doubled.
The scale comes from two known distances. On the long-lens strip, Bratton Castle to Stonehenge (23.8 km) gives 1.32 m of ground per scanned pixel. On S 102, Old Sarum to Figsbury Ring (5.2 km) gives 3.22 m per pixel.
The frames lean about 15° off the line of flight, the drift of an aircraft crabbing into a crosswind. At exposures 129 and 130, over Amesbury, they swing round by 12° and then 16°: the aircraft turned south over the Avon towards Clarendon and Redlynch.
What the interpreters wrote
The pencil notes on the backs name each frame by its map sheet and by the most prominent landmark in it. In every case read, that landmark is a prehistoric monument:
Back of print L 116: "Bratton Cas. b. Bratton sö Bristol / Bl. 32." Agfa-Lupex paper. NARA RG 373, GX 10484.
PrintPencil noteMeaning
L 116Bratton Cas. b. Bratton sö Bristol Bl. 32Bratton Castle, near Bratton, south-east of Bristol, map sheet 32
L 126Stonehenge Salisbury; "ca. 12 km nw. Salisbury"Stonehenge written and struck out
L 128Tumuli b. Stonehenge … nnw Salisbury Bl. 33Barrows near Stonehenge, struck out
S 097Yarnbury Castle nw Salisbury Bl. 33Yarnbury hillfort
S 102Old Sarum u. Figsbury Rings bei Salisbury Bl. 33Old Sarum and Figsbury Ring
"Bl. 32" and "Bl. 33" are the same map-sheet numbers as the "Engl. Bl." references on the Luftwaffe target dossiers. None of the notes read names an airfield or a camp, though military sites on the Plain lie in the same frames.
Stonehenge
Stonehenge on L 127, 29 November 1940, shown as flown (top of picture to the south-east). The old A344 runs beside the stones. Luftwaffe, NARA RG 373, GX 10484.
Stonehenge falls on only one long-lens frame, L 127, close to its edge, and on S 098. The bank and ditch, the sarsen circle, the A344 beside the stones and the custodian's buildings are all clear. On the frames either side, 126 and 128, the interpreter wrote "Stonehenge" and then struck it out. The stones are not in either picture.
The aircraft
No record yet found names the aircraft, its unit or its crew. NARA's item records give none, and NCAP's Luftwaffe collection is uncatalogued at sortie level. The prints narrow it down. Lenses of 50 cm and 20 cm are the standard pair for German long-range reconnaissance, usually the Rb 50/30 and Rb 20/30 on 30 × 30 cm film. With that film, the ground each frame covers puts the aircraft about 7,800 m above the ground. Spacing and clock together give a ground speed near 500 km/h. Both fit a Ju 88 reconnaissance aircraft with a tailwind, or possibly a Do 215. Aufklärungsgruppe 123, Luftflotte 3's reconnaissance group in the west, was flying Ju 88s over southern England that month and lost two of them, at Parkstone on 14 November and at Coates on 24 November. All of this is an estimate; the film says so.
Notes on the film
The landscape film runs at about four times real speed and is turned so that the aircraft flies left to right. Each frame is captioned with its exposure number, NARA's nearest place name and its clock reading. It pauses on Bratton Castle and Stonehenge, which are shown from the original full-resolution scans. The missing exposure 131 is a short black gap. The short version opens on Stonehenge and then flies from Avoncliff to Bratton. The music is original.
For the purist: the director’s cut, the photographs alone at twice real speed. View on YouTube full-screen for the best experience.
A fascinating then and now comparison companion video:
Sources
National Archives and Records Administration. German Flown Aerial Photographs, 1939–1945. RG 373, series NAID 306065; file units GX 10484 SG. catalog.archives.gov/id/306065
National Archives and Records Administration. Target Dossiers Pertaining to the British Isles, 1938–1945. RG 242, series NAID 3371016. catalog.archives.gov/id/3371016
National Collection of Aerial Photography. German Air Force (Luftwaffe), GB 551 NCAP/4. ncap.as.atlas-sys.com
Luftwaffedata Wiki. Aufkl. Gr. 123 1940. luftwaffedata.co.uk
Luftwaffedata Wiki. Aufklärungsgruppe Ob.d.L. luftwaffedata.co.uk
Daw, T. 2026. The Luftwaffe's Wiltshire. sarsen.org; map at wiltshire-luftwaffe.netlify.app
Daw, T. 2026. The Flight of GX 10135: 18 August 1940. sarsen.org
All photographs: Luftwaffe, 29 November 1940; US National Archives, RG 373, GX 10484, listed as Use: Unrestricted. Frame matching, measurements and film: T. Daw. Methods and scripts: github.com/TimDaw37/wessex-films.

https://www.sarsen.org/2026/10/the-flight-of-gx-10484.html

Verbum sapienti: a word to the wise Professor Peter Kokelaar has ...

2026-10-16T04:39:44Z

Verbum sapienti: a word to the wise

Professor Peter Kokelaar has earned a distinguished reputation as a volcanologist, and that is exactly why his recent essay arguing that the Stonehenge bluestones came "mostly by ice" is worrying. I raise it in the spirit of a friendly warning: a record built over a career deserves better than to be spent on claims that don't survive a first look.
The "Boles Barrow Bluestone" in Salisbury Museum - T. Daw
Take his "smoking gun", the Boles Barrow stone, which he calls a well-rounded erratic. Anyone can turn it round on the Sketchfab 3D model and see that it is squared off with dressed sides, worked by people rather than shaped by ice. Its link to the barrow isn't documented anyway. The Newall boulder, which he sets aside, has been discussed in detail by Bevins et al. (2023).
To say there is no evidence for neolithic human transport of monoliths is just absurd.
Even great minds can be led astray when they step outside their own field. Arthur Conan Doyle, creator of the most rational detective in fiction, staked his name on the Cottingley Fairies photographs, and that is now what many people remember him for. Peter is a far better scientist than that, and I hope he will step back before the ice-transport case becomes his Cottingley.
Disclosure: I am a co-author of Bevins et al. 2023.

https://www.sarsen.org/2026/10/verbum-sapienti-word-to-wise.html

The Flight of GX 10135 - Down the A303 on an August day, 1940 On ...

2026-10-16T03:45:45Z

The Flight of GX 10135 - Down the A303 on an August day, 1940

On 18 August 1940 a German reconnaissance aircraft crossed south Wiltshire with three cameras running. From near Mere it followed the line of the A303 east past Chicklade, Wylye and Yarnbury Castle to Winterbourne Stoke, passed Stonehenge, turned south over the Avon and ran down past Old Sarum to Salisbury. Its prints are in the US National Archives. Joined in order, they make a strip some 45 km long, and the films below fly it again. A companion to The Luftwaffe's Wiltshire and to the film of sortie GX 10484, flown three months later.
Sortie GB 956
NARA files the prints as box GX 10135. The titling strip on each reads GB 956 with the camera letter and the date, and each clock dial is pencilled "18.8." with the camera letter. The day is the one later called the Hardest Day of the Battle of Britain: the Luftwaffe made heavy raids on Kenley, Biggin Hill, West Malling, Hornchurch, North Weald, Ford, Gosport, Thorney Island and the Poling radar station. No record found links this sortie to those raids, and none records reconnaissance over Wiltshire that day.
Three cameras
Three cameras ran together, and all three survive for this stretch:
L, a long lens of 502.48 mm: 17 frames, exposures 27–43, each about 5 km across on the ground.
R, a second long lens of 505.13 mm aimed off to one side: 12 frames, exposures 19–30. Its frames overlap the L frames by only 5–25%, and they are not used in the films.
S, a wide-angle camera: 9 frames, exposures 16–24, each about 13–15 km across. Each S frame contains three to five whole L frames, at roughly 2½ times less detail.
The L run has a gap. Over the Plain the aircraft turned through about 110°, and L 36 and L 37 do not overlap their neighbours. The S frames do: the nine of them join without a break from Mere to Downton, across the turn. So the films fly over the S strip and use the L frames for the close views, at Yarnbury Castle, Stonehenge and Salisbury Cathedral.
The nine wide-angle frames joined, north up. Places marked at their Ordnance Survey positions. Luftwaffe, 18 August 1940, NARA RG 373, GX 10135.
The camera clocks
On the L and R prints the dark mark near twelve is the hour hand; the minute hand is hidden under the pencilled date. The S clocks show both. Their minute hand moves from about 37½ on S 16 to about 44½ on S 24: roughly a minute between wide frames, and seven to nine minutes for the whole run. The hour hand stands just short of twelve. Neither the time zone nor whether the clocks were set together is stated on the prints.
The S-camera clock on the first and last frames, S 16 and S 24. NARA RG 373, GX 10135.
The centres of the S frames are 4.9–7.1 km apart, 45 km in all. Over seven to nine minutes that is a ground speed of roughly 300–390 km/h. If the film is 30 × 30 cm, as on GX 10484, the 5 km cover of the 502 mm lens puts the aircraft about 8 km above the ground. Both figures are estimates; no record names the aircraft or its unit.
Along the A303
The road was numbered the A303 on 1 April 1933, so it carried that number on the day of the flight. In 1940 it still ran through Wylye, bypassed in 1975, and through Amesbury, bypassed in 1969. For the first half of the run the aircraft follows it closely, which is why the films use it to keep the viewer oriented.
Yarnbury Castle
Yarnbury Castle, north up, from L 34. The A303 passes the southern edge of the hillfort. Luftwaffe, 18 August 1940, NARA RG 373, GX 10135.
The Iron Age hillfort lies beside the A303 west of Winterbourne Stoke. Next to it, white lines of freshly dug chalk mark army training trenches. The ground was commandeered by the Army in 1916, and on these prints the trenches are still bright, so the digging was recent.
Stonehenge, August 1940
Stonehenge, north up, from L 37. Luftwaffe, 18 August 1940, NARA RG 373, GX 10135.
Stonehenge falls on L 37, the frame at the turn. Beside the stones run the A344 and the old crossroads with the byway that was moved west in 1967. The 1917 aerodrome to the west closed in 1921; its buildings were demolished from 1927 and cleared by the early 1930s, and the Stonehenge Café and the custodians' cottages went in 1938. By August 1940 only the marks of these buildings remained. In high summer the grassland around the stones is pale and the tracks across it stand out, against the dull ground of the November photographs of GX 10484.
Old Sarum and Salisbury
After the turn the aircraft ran south down the Avon. Old Sarum, the Iron Age hillfort and site of the first Salisbury, passes on the way; beside it lay RAF Old Sarum, where No. 225 Squadron had been based since June 1940. The run ends over Salisbury, the cathedral and its Close in the middle of the frame, and continues south towards Downton.
Salisbury Cathedral and the Close, north up, from L 40. Luftwaffe, 18 August 1940, NARA RG 373, GX 10135.
Joining the frames
The nine S frames were matched on their common ground and fitted together in one adjustment; neighbouring frames agree to 2–4 scanned pixels for most pairs, 5–9 near Mere. Each L frame was then placed on the S strip, to within about a pixel of the S scan, so the close views drop into the wide flight in the right place. To label the films and set the north arrow, the strip was matched to modern imagery on some 750 field edges and hedgerows, to within about 70 m over most of it and 200 m at worst. Each part of the strip comes from one photograph only, so nothing is doubled at the seams.
Notes on the films
Three versions. The captioned film (3:05) names places as they pass and has short notes on the cameras, the road, Yarnbury, Stonehenge, Old Sarum and the cathedral. The director's cut (2:41) is the photographs alone, with a north arrow. The short (0:40) opens on Stonehenge, flies the A303 to Yarnbury and ends over Salisbury. All three run at four to five times real speed. The backs of the GX 10135 prints have not been scanned, so there are no interpreters' notes to quote. The music is original.
Sources
National Archives and Records Administration. German Flown Aerial Photographs, 1939–1945. RG 373, series NAID 306065; file units GX 10135 SG and SK. catalog.archives.gov/id/306065
English Heritage. Stonehenge in the 1930s and 40s: protecting the landscape. english-heritage.org.uk
Historic England. Stonehenge Aerodrome and the Stonehenge Landscape. Research Report 7/2014. historicengland.org.uk
Battle of Britain 1940. Sunday 18 August 1940. battleofbritain1940.com
Wikipedia. A303 road; Stonehenge Aerodrome; Old Sarum Airfield; Yarnbury Castle; Wylye. en.wikipedia.org
Daw, T. 2026. The Luftwaffe's Wiltshire. sarsen.org; map at wiltshire-luftwaffe.netlify.app
All photographs: Luftwaffe, 18 August 1940; US National Archives, RG 373, GX 10135, listed as Use: Unrestricted. Modern imagery (Esri) was used for matching only and is not reproduced. Frame matching, measurements and films: T. Daw. Methods and scripts: github.com/TimDaw37/wessex-films.

https://www.sarsen.org/2026/10/the-flight-of-gx-10135-down-a303-on.html