Calculating distance between two Points ( Longitude and Latitude) in SQL using GEOGRAPHY type
With geography datatype you can create system where you can filter locations on bases of distance between them. Also it make very easy to calculate distance between 2 location points. Along with that you can use any GPS standard system using SRID parameter in methods offered by Geography datatype.
For script check below link:
Building system where you can search locations near by N miles or kilometer