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

[lambi at ucar.edu]

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