[gdal-dev] gdalwarp cutting off projected image

Steve Gaffigan gaffigan at sfos.uaf.edu
Wed Dec 10 00:37:35 EST 2008

> I have established the problem is the logic that computes the desired
> extent of the output file.  It walks the edges of the input file,
> transforming to WGS84 and ends up with incomplete extents because there
> is no recognition that there is a topological discontinuity in the
> transformation (the pole issue).


I wonder if a solution to this problem of detecting the vertical
discontinuity is solved using the following logic:

"Walk the edges of the the input file, reprojecting to get the extents for
the output, as usual.  Then repeat the process along the edges of an
interior rectangle.  If the output extent corresponding to the interior
source rectangle has a more extreme northing extent than that from the
original rectangle, then extend the output extent to the
southernmost/northernmost extreme and the entire easting extent."

I make extensive use of the below patch to Mapserver, which is based on
this logic, and which works well for combinations of source and
destination projections in geographic, Albers, polar stereographic, and
equidistant cylindrical.


If there are limitations/errors in this assumption which are obvious to
you on anyone on the list, I'd appreciate your expertise on the issue.

Steve Gaffigan

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