Geo_convert is a project mainly written in Ruby, it's free.
Module to provide conversions between LatLong and EastingsNorthings
h1. GeoConvert
h2. A Module to convert coordinates
This is very much a work in progress. The LatLong -> UTM conversion is not working at all.
h3. Background
h3. Source
The calculations in this module are taken entirely from the Geographic/UTM Coordinate Converter page by Chuck Taylor: http://home.hiwaay.net/~taylorc/toolbox/geography/geoutm.html Any errors in the calculations are mine.
h2. Usage
require 'geo_convert'
easting = 717443 northing = 6.39756e+06 zone = 50 southern_hemisphere = true
GeoConvert.utm_easting_northing_to_latlong(easting, northing, zone, southern_hemisphere)