[Gdal-dev] Projection Parameters

[Frank Warmerdam]

Grabowski, Hank wrote:
> Hey Frank,
> 
> I was just using the Validate method in a preliminary pass.
> Unfortunately if I simply ignore that step and let OGR try and reproject
> the data anyway, I don't get a valid reprojection.  From what I can tell
> the importFromESRI function is calling the morphFromESRI function, but
> it isn't successfully remapping the parameters.  The projection I'm
> trying to import is a World Mercator projection.  Is there a csv
> datafile, that I see references to in the code, that I should have
> installed?  I'm thinking the answer is no, because the IsAliasFor method
> used in ValidateProjection has all the necessary values.  At one point
> are these parameters supposed to be swapped or re-interpreted during the
> morphFromESRI or importFromESRI function?

Hank,

The corresponding aliasing logic in actual use is embedded as code in
the GetProjParm() method.  There, for instance, if Latitude of Origin
is requested but not found, it will also try latitude of center.

I see that the rules in this method don't exactly match the alias list
in the validate code, but likely should.  If you can submit a bug report
with the original ESRI .prj file I can try to track down what is happening
and generalize the logic.

Code that converts to other formats, such as PROJ.4, use GetProjParm()
with the expectation that it will know something about common aliases.

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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