you could reduce the number of letters required without losing accuracy by being less precise at the poles (a simple lat/lon is over-precise there because the l

you could reduce the number of letters required without losing accuracy by being less precise at the poles (a simple lat/lon is over-precise there because the lines of longitude get closer together). it would require a slightly more complex transformation, but not by much (for example, you could make it uniform in lambert equal area - http://en.wikipedia.org/wiki/Lambert_cylindrical_equal-area_projection http://en.wikipedia.org/wiki/Lambert_cylindrical_equal-area_...). in other words, by taking the sine of the latitude and then converting that to letters you can truncate more digits (because you the resolution you need at the equator and at the poles is the same). also, i suspect geohash could be improved by using a fractal approach like http://xkcd.com/195/ http://xkcd.com/195/ (http://blog.xkcd.com/2006/12/11/the-map-of-the-internet/ http://blog.xkcd.com/2006/12/11/the-map-of-the-internet/) which should reduce the need for worrying about boundaries (ie make things more efficient). in fact, you could combine the two.... [edit: although the fractal approach with equal area would mean that the distances of "nearby" points changed with latitude; it would be better to use an equal-distance projection.]