[thelist] Proximity/Radius searching?

[Dan McCullough]

I have one that uses log and lat coordinates I'll have to zip it up
and export the database.

On 7/22/05, Jeff Howden <jeff at jeffhowden.com> wrote:
> Erik,
> 
> ><><><><><><><><><><><><><><><><><><><><><><><><><><><><><
> > From: Erik Heerlein
> >
> > I believe once I saw some code to do that which was
> > basically a poor man's way of doing it without map
> > coordinates. Since zip codes are bunched together, 29412
> > is next to 29487 and so on, you search for matches
> > between zip codes. Stores with zip codes between 90210
> > and 90300 are close together. So you add 100 and subtract
> > 100 to the customers zip code that they entered and you
> > search in that range.
> ><><><><><><><><><><><><><><><><><><><><><><><><><><><><><
> 
> Your method is based on a very flawed assumption, seemingly supported by
> examination of only a tiny subset of the data.  Zip codes do *not* work that
> way.  Anybody that provides a paying client with a dealer locator based on
> this logic is doing themselves and their client a major disservice.
> 
> Even your example zip codes expose the flaw in the logic.  By your method,
> you'd be missing out on 90069 (1.47 miles away), 90067 (1.93 miles away),
> 90048 (1.96 miles away), 90035 (2.49 miles away), 91614 (3.72 miles away),
> 91423 (4.93 miles away), etc.  In fact, in some areas like zip code 90210
> there are over 170+ zip codes within a 10 mile radius.
> 
> http://zipfind.net/Results.aspx?ZIP1=90210&RADIUS=10&TYPE=RADIUS
> 
> More in a post I made to the list almost 4 years ago:
> 
> http://lists.evolt.org/archive/Week-of-Mon-20010924/058003.html
> 
> Enjoy,
> 
>  [>] Jeff Howden
>     jeff at jeffhowden.com
>     http://jeffhowden.com/
> 
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