Re: Zip Code Proximity search

[Felix Sheng]

I built a similar app where I needed to find nearby things in zip, but I found the pre-built range lookup table path a bit restrictive. The tack I took was to essentially draw a very rough square surrounding the middle point - a high and low latitude and longitude that I knew to contain the entire circle. (this is easy to come up with if you assume the earth is flat in the area you're looking - if your workspace is america sized, it works fine. :). Then you can easily do a select for all the zips in the square and if you want you can further use great circle, haversine, etc... to more accurately pare it down. But once you've drawn your rough rectangle the number of zips you have to contend with is *much* more manageable.

The nice thing about this is it puts most of the work (which isn't that much) into the app and out of the db. Which is something I tend to like.

felix