There already is a geohash tag, which Amethyst supports already.
Maybe this is what you're looking for?
Felix
npub1z9…zvycf
2024-09-06 12:58:18
in reply to nevent1q…zzh6
Author Public Key
npub1z9n5ktfjrlpyywds9t7ljekr9cm9jjnzs27h702te5fy8p2c4dgs5zvycf