[Proj] Conversion to UTM

Frank Warmerdam warmerdam at pobox.com
Fri Jan 5 10:57:13 EST 2007

Mathias bavay wrote:
> Hi!
> I am wondering: why is the UTM zone not computed by cs2cs when 
> converting coordinates to utm? Is it because a specific algorithm would 
> have to be implemented for each projection?


Three reasons:
  1) It doesn't fit the model.  Different UTM zones are different coordinate
     systems, and the proj interface is setup such that the output coordinate
     system is initialized in advance.

  2) There are perfectly legitimate reasons to use a UTM zone somewhat outside
     it's defined area of appropriateness.

  3) There would be know way to know what UTM zone was used for a set of
     UTM coordinates coming out of cs2cs so the projected locations essentially
     would become meaningless.

It would be nice to have a function to suggest the most appropriate UTM zone
for a given lat/long location but this is not trivial if you want to apply
the special zone mappings in Scandinavia (and perhaps other places).

> Mathias
> PS: I am working on a qt GUI for cs2cs. I should be able to release its 
> first version soon! (my goal is to make something useful, convenient and 
> that casual users can use without making obvious mistakes)

Sounds cool.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org

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