Converting UTM coordinates into latitude and longitude coordinates

The coordinates used in the raw GPS data are sometimes in the UTM (Universal

Transverse Mercator coordinate system) format.

There is a need to convert them into into latitude and longitude coordinates for reverse-geocoding with Google Map API.

There may be many ways of doing the conversion. The following are two ways:

1. The method introduced by Salkosuo (java lib)http://www.ibm.com/developerworks/java/library/j-coordconvert/
2. Postgis extension provides in-database conversion function.