zip code search

[Steve]

Hi-
I'm looking to make an asp.net application that will allow site visitors to
enter their zip and find the closest dealer in our database. Funny thing
is... I have NO idea how this is done! I figure there must be a way to
query the DB for zips that are in the same state as the seach zip, then
enumerate over all of those and calculate the distance from each one storing
the shortest ones. But how, is there a service you need to subscribe to?
Anyone have some pointers?

 

[Karl Seguin]

Steve:
Normally what you can do is measre the distance between two geographical
points (latitude/longitude). This is pure mathematics. You must map your
zip code to lat/long coordinates. You can find databases for this online.
One such vendor is http://www.zipcodeworld.com/ (they also have the source
code for determining the distance between two coordinates online:
http://www.zipcodeworld.com/samples/distance.cs.html but it isn't free to
use, I don't think).

There are plenty of open source projects written in a veriaty of languages.
The only C# one I was able to quickly find was:
http://www.codeproject.com/csharp/ZipCodeUtil.asp

Karl



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come!)

 

[jhcorey]

What you have to do is find a function that you can use in your sql
query to calculate distance -- if you google the sqlserver.programming
group I'm sure you'll find one -- I've done this but I don't have it
handy.
Then your query looks something like this:

select myCalculation(lat,long,dealerLat,dealerLong) as Distance,
dealerName from myTable
order by Distance

(obviously a prerequisite would be getting the lat/long for the zips).

 

[Steve]

right, that is proving to be the missing piece that I was looking for, the
lat/long data for the zips. MS has mappoint that they sell as a web
service, but I was hoping there would be a free service. I will look at the
links that Karl posted.

Thanks for the help guys!

 

[jhcorey]

Just happened to have been looking at this article. Says the download
includes a database with zip codes and lat/long.
http://www.eggheadcafe.com/articles/20050514.asp

 

[Steve]

nice! Thanks!!