[gdal-dev] building geotransform with lower left and upper right coordinates

Brian Case rush at winkey.org
Mon Feb 13 12:44:31 EST 2012


After some thought your image might not be bottom up. if thats the case
calc the origin the way you did before, but don't convert back to lat


On Mon, 2012-02-13 at 05:40 -0700, lambi at ucar.edu wrote:
> Hello,
> I have a raster where I know the projection and the lower left and upper
> right coordinates and pixel size but I don't know the upper left
> coordinate.  It is a lambert conformal conic projection:
> "+proj=lcc +lon_0=95W +lat_0=25N +lat_1=25N"
> where the lower left is -113.1333, 16.3691
> upper right is -49.385, 57.289
> dx/dy is 1015.875 (m)
> width/height is 5120
> I've tried transforming the lower left lat/lon to lcc projection, adding
> dy*height and then converting back to lat/lon (and a few variations of
> this) but I can't seem to get a proper answer for what the upper left
> should be so I can build a proper geotransform for this dataset.  I've
> tried adding two GCPs for these points but gdalwarp says it doesn't have
> enough points to complete the warp.
> How can I find the upper left with the given information so I can build
> the geotransform?
> Any help is greatly appreciated!
> Brice
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