Geohash for spatial index and search. Nice, clear explanation of what a Geohash is. It’s a way of encoding a lat/lon position as a short string, with the useful property that similar co-ordinates with more or less significant figures share a common prefix in their geohash.
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The common prefix property doesn't apply for locations either side of Greenwich!
Thanks for the link. I was inspired and thought I'd finally write up a similar implementation I did a while ago. Probably not as advanced, but might be interesting since it's very easy to understand.
http://fukamachi.org/wp/2008/06/09/geohashing-usin g-matrices-in-ruby/
Sho - 8th June 2008 19:17 - #