The What3Words geocoding service assigns a three-word mapcode to every three-square-metre patch on the planet, the premise being that three words are easier to remember and share than longitude and latitude to the equivalent decimal places. But the main complaint about What3Words (apart from the proprietary nature of its algorithm and database) is that it’s possible to get even those three words confused, especially in contexts where plurals and homophones may not be heard clearly, or where similar combinations of words are close enough to each other that they can be mistaken for each other. There’s actually an entire website dedicated to chronicling errors in W3W.

W3W maintains that their algorithm keeps similar combinations “so far apart that an error is obvious. We also worked hard to remove homophones and near homophones like sale and sail.” They rate the the chance of two confusing combinations appearing close enough to be unclear at about 1 in 2.5 million. But in a new analysis of the algorithm, currently in preprint, computer scientist Rudy Arthur argues that despite W3W’s claims this chance of confusion is far higher, and warns against adopting W3W as critical infrastructure (it’s used by emergency services, particularly in the U.K.) without testing and comparing against available alternatives. [The Register]

Previously: What3Words Hasn’t Had the Greatest Couple of Months: A Roundup.