require 'geoutm'

coordinate = 100.0, 100.0
to_utm = coordinate.to_utm
and_back = utm_coord.to_lat_lon


gem install geoutm


This gem translates between latitude and longitude coordinates to Universal Transverse Mercator(UTM) coordinates. The first kind is generally reported by GPS units, while the second is useful as they are represented in meters, thus making distance calculations easier.

For more information please refer to


A description of the available ellipsoids and sample usage of the conversion routines follows


Ellipsoids describe the shape of the earth used to calculate the UTM grid. As a default, WGS-84 is selected, but any of the following ellipses may be used:

  1. Airy

  2. Australian National

  3. Bessel 1841

  4. Bessel 1841 Nambia

  5. Clarke 1866

  6. Clarke 1880

  7. Everest 1830 India

  8. Everest 1830 Malaysia

  9. Everest 1956 India

  10. Everest 1964 Malaysia and Singapore

  11. Everest 1969 Malaysia

  12. Everest Pakistan

  13. Fischer 1960 Mercury

  14. Fischer 1968

  15. GRS 1967

  16. GRS 1980

  17. Helmert 1906

  18. Hough

  19. Indonesian 1974

  20. International

  21. Krassovsky

  22. Modified Airy

  23. Modified Everest

  24. Modified Fischer 1960

  25. South American 1969

  26. WGS 60

  27. WGS 66

  28. WGS-72

  29. WGS-84

When specifying the ellipsoid as a parameter, you may use an instance of the GeoUtm::Ellipsoid class, a string containing the name above, or alternatively just a symbol (eg. :wgs84). The name is not case sensitive and symbols are allowed. Spaces and - are ignored.

Latitude / longitude to UTM conversion

Latitude values in the southern hemisphere should be supplied as negative values (e.g. 30 deg South will be -30). Similarly Longitude values West of the meridian should also be supplied as negative values. Both latitude and longitude should not be entered as deg,min,sec but as their decimal equivalent, e.g. 30 deg 12 min 22.432 sec should be entered as 30.2062311

The ellipsoid value should correspond to one of the numbers above, e.g. to use WGS-84, the ellipsoid value should be 23

For latitude 57deg 49min 59.000sec North

longitude 02deg 47min 20.226sec West

using Clarke 1866 (Ellipsoid 5)

utm =, -2.788951667).to_utm(Ellipsoid::lookup('clarke 1866'))

returns  = 30V
utm.e     = 512533.364651484
utm.n     = 6409932.13416127


This gem is heavily inspired and to a large extent also copied directly from by the Perl library Geo::Coordinates::UTM written by Graham Crookham. Graham Crookham, [email protected]

Ruby port by Tallak Tveide, Erling Linde 2009/2011


Copyright © 2000,2002,2004 by Graham Crookham. All rights reserved.

This package is free software; you can redistribute it and/or modify it under the same terms as Perl itself.