[FWTools] Van der Grinted apparent projection error

[Conor O'Donoghue]

Hello,
I type gdalwarp -t_srs "+proj=vandg" 15deg02grid.tif 15deg02vandggrid.tif
The input file is a whole world TIFF  (15degree raster grid, 5400 x 2700 pixels) and no compression.

The output TIFF has two errors.
1) The image (map) that goes beyond 180 degrees to fill the corners of this Van der Grinten tiff is incorrect in latitude, as evidenced by the abrupt change of the angle of the latitude lines.

2) A band of longitude (approx 175 degrees to 180 degrees west arc) is solid black where there should be projected image.

I would be happy to supply the image that is self explanatory but not sure if images are allowed.

Con anyone help lead me to the solution?
Thanks
Conor
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