I grabbed a database of the zip codes and their langitudes/latitudes, etc from this This page. It has got the following fields:
ZIP, LATITUDE, LONGITUDE, CITY, STATE, COUNTY, ZIP_CLASS
The data was in a text file but I inserted it into a MySQL table. My question now is, how can i utilise the fields above to calculate the distance between two zip codes that a user can enter on the website? Working code in PHP will be appreciated
This is mike's answer with some annotations for the magic numbers. It seemed to work fine for me for some test data:
function calc_distance($point1, $point2)
{
$radius = 3958; // Earth's radius (miles)
$deg_per_rad = 57.29578; // Number of degrees/radian (for conversion)
$distance = ($radius * pi() * sqrt(
($point1['lat'] - $point2['lat'])
* ($point1['lat'] - $point2['lat'])
+ cos($point1['lat'] / $deg_per_rad) // Convert these to
* cos($point2['lat'] / $deg_per_rad) // radians for cos()
* ($point1['long'] - $point2['long'])
* ($point1['long'] - $point2['long'])
) / 180);
return $distance; // Returned using the units used for $radius.
}