[Proj] how to compare 2 proj4 definitions? or: how to normalize proj4 definition?

Frank Warmerdam warmerdam at pobox.com
Wed Feb 28 17:16:38 EST 2007

Gerald I. Evenden wrote:
> On Wednesday 28 February 2007 12:50 pm, Frank Warmerdam wrote:
>> Sergey Spiridonov wrote:
>>> Hash: SHA1
>>> Hi
>>> I need to compare two proj4 definitions. It is clear that I can not
>>> compare them as strings, because order of the parameters can be changed,
>>> floats can be in different format, there can be various units.
>>> Is there any normalization function available. If not, I will write one.
>> Sergey,
> I was totally confused by the above request and thus chose to ignore it.  But 
> I was confused even more by the response so please forgive my added notes.


I believe Sergey is looking for a way of comparing PROJ.4 projection
definitions to see if they are equivelent.  By normalization he means
putting the coordinate system definition into a "normalized form" such
that two equivelent coordinate system definitions will have the same
string representation.  I'm not sure if this is a proper use of the word
normalize, but it was at least clear to me.

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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