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

Brian Case rush at winkey.org
Mon Feb 13 12:31:37 EST 2012


with that projection the origin should be in meters. convert the ll to
meters and try setting dy to dy * -1


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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