Re: Script for "Dealer Locator"

From: Nikolai Chuvakhin (nc_at_iname.com)
Date: 07/05/04 

Date: 5 Jul 2004 10:59:20 -0700

galsaba@aol.com (Galsaba) wrote in message
   news:<20040704063732.04299.00001036@mb-m15.aol.com>...
>
> I am trying to find a script to a "dealer locator" or "find a store
> near you".
>
> I will have two tables. One will include all US and Canada ZIPs
> including lat and longtitudes. The other one is a table of our
> dealers (or store) including thier ZIP codes.
>
> When the user enters his ZIP code, the application needs to check
> (based on the lat and long) if there is a dealer in a 30 miles
> radious. After the application finds the list of all the dealers
> withing this radius, it will send a list with their name, address,
> and the distance from the (ZIP of ) user.

The formula to find the distancebetween two points given their cordinates
is:

   $distance = $r * acos(cos($lat1) * cos($lon1) * cos($lat2) * cos($lon2) +
                         cos($lat1) * sin($lon1) * cos($lat2) * sin($lon2) +
                         sin($lat1) * sin($lat2));

   where:

   $r -- radius of the Earth
   $lat1 -- latitude of point 1 in radians
   $lon1 -- longitude of point 1 in radians
   $lat2 -- latitude of point 2 in radians
   $lon2 -- longitude of point 2 in radians

You can produce an SQL version of this formula and use it for retrieval
of distances and in the WHERE clause.

Cheers,
NC

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