A lot of good ideas here, but I'd shoot for a slightly larger number here than 100. You get a polynomial effect here, where a word added to list A gets you (the

A lot of good ideas here, but I'd shoot for a slightly larger number here than 100. You get a polynomial effect here, where a word added to list A gets you (the length of list B x the length of list C) more combinations--there's a lot of payoff to even adding just a few more words to each list. The surface area of the earth is about 200 million sq miles, so 1 million unique points gets you 200 sq miles each, not 20. That's 5,575,680,000,000,000 square feet. 40,000 words per list (the length of the W3W list) gets you down to about a 87 square foot (around 9ft x 9ft) area with three words. I tend to agree with you that 9ft x 9ft is smaller than necessary for most purposes. If we target a 16ft x 16ft area (5m x 5m for those using metric), we get that with three word lists of 28,000 words. Using six words (three nouns for general area, plus three adjectives for precision), word lists of 168 words are adequate. I'm not completely convinced that the larger areas are ever useful, however. By going to just 4 words, we can achieve the 16ft x 16ft area with four lists of 2200 words. Those lists are short enough to plausibly check for sound-alikes, enough words exist to have four separate word lists, and have a shorter resulting location phrase. I'm also not convinced that the set being order-free is really necessary. Transposition errors seem more likely in longer data sets than three words (hence even/odd word lists in the PGP word list).