[Proj] Using a GDAL-generated NTV2-file
j.l.h.hartmann at uva.nl
Tue May 24 04:51:39 EST 2011
On 05/21/11 18:06, Frank Warmerdam wrote:
> I believe the problem is that the test.tif is south up. The NTv2 reader
> in PROJ determines the size based on the extents and pixel size and gets
> mixed up as the extents are upside down. You can flip test.tif with
> gdalwarp test.tif northup.tif
Yes, now it works. Just to be sure: is the result of the flipping
correct? The tif file was created from two point lists, each with a
lat-lon coordinate and the displacement in arcseconds. Gdal_grid
converted the lists into two grid files, with the upper boundary having
a smaller latitude than the lower coordinate. That's OK, as latitude
values decrease when going north, in contrast with projected coordinates.
Now, what happens when I use gdalwarp on this file? Is the complete file
mirrored? Are the displacements at the right geographical location?
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