This program calculates the distance between two zip codes in the United States. The sub-routines included in the code can be used to calculate any distance between latitude and longitude coordinates.
The package includes data for the US, the script includes two sub-routines, one gets the coordinates and city name, the other calculates the distance between two points.
The result should be very precise because the calculation takes into account the fact that the earth is not a perfect sphere.
Note that the data provided by the census bureau has not been updated lately and some zip codes might be missing or corrupted, causing a sporadic server error. The ASCII data file can easily be incorporated into Geozip. The provided data file is being orporatedegularly.