Logitude & Latitude Based Proximity Searching
Hi,
I want to do proximity searching based on longatude and latatued over the whole world. Basically I want to be able to have users find all other uses in a database that are close by (say 25 miles or something). So in some places the regions will be sparse and other densly populated.
Initially I don't mind if the algorithem is very accurate as long as it is fast. When I say 25 miles I wouldn't mind if it picked up some from 30 miles or something. I could always perfrom slower, more exact calculations after I've found the nearest users anyway.
One technique I've heard mentioned (if I got the idea right) is deviding the world up into grids. I think the idea was that you, for example, have grids 5 miles square and if you fell into that grid it would be stroed in the database. You would then select anyone from that grid or surrounding grids.
Does anyone know anything about this technique or other techniques? Thanks.
-Sam
