[Gdal-dev] gdalwarp failing on proj=ortho

[Frank Warmerdam]

Tyler Mitchell wrote:
> Sorry to bring up orthographic projections again, I know you looked into these 
> earlier this year.  I really want to show this one off though!  I'm trying to 
> convert a lat/long image into ortho - but I think I'm missing something.
> 
> Here is my command line:
> 
> gdalwarp -s_srs '+proj=latlong' 
> 	-t_srs '+proj=ortho +ellps=WGS84 +lat_0=60 +lon_0=-95' 
> 	globe.tif globe_ortho.tif
> 
> The output error I get is:	
> 
> ERROR 1: tolerance condition error
> ERROR 1: GDALWarperOperation::ComputeSourceWindow() failed because
> the pfnTransformer failed.
> 
> I'm running proj-4.4.7 and gdal from cvs a couple weeks ago.  Any ideas why 
> this doesn't work?

Tyler,

The tolerence condition error is coming out of PROJ.4. I don't know exactly
what it means, but I presume it indicates some sort of mathematical error
in transforming "over the horizon" or off the earth.

If you can make globe.tif available to me I can see why gdalwarp isn't more
adaptive when only subregions of the target area support reprojection.  I
did a bunch of work on global scale transformations in MapServer but I don't
think the same capabilities were implemented in GDAL itself.  In fact, I
would appreciate it if you could submit this problem via the GDAL bugzilla.

I would add that you should specify an ellipe or datum with all projections
that don't implicitly contain one.  For instance you should have
'+proj=latlong +ellps=WGS84' in this case.  I doubt this has anything to do
with the problem though.  I presume it is using WGS84 internally as a default.

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