I spent a few minutes exploring a similar. Using the EFF wordlist (7776 words designed to be unambiguous)[1] you should be able to get down to about 100m^2 blocks (good enough for SAR), the BIP39 word list (2048) is a bit too resolution, but is a lot easier to pronounce, maybe worth some encoding shenanigans to get it to work).
For my POC, I also used a simple 1D hilbert curve. Running a simulation and plotting the words, you actually get pretty decent resolution, and it's even alphabetical by distance. Output from simple demo w/ BIP39 (math might not be correct): https://ibb.co/MnmcRFk but you can see that the word order actually make sense (although "winner" and "winter" are too phonetically similar, but still, gets the point across).
For my POC, I also used a simple 1D hilbert curve. Running a simulation and plotting the words, you actually get pretty decent resolution, and it's even alphabetical by distance. Output from simple demo w/ BIP39 (math might not be correct): https://ibb.co/MnmcRFk but you can see that the word order actually make sense (although "winner" and "winter" are too phonetically similar, but still, gets the point across).
[1] https://www.eff.org/deeplinks/2016/07/new-wordlists-random-p...