Level 2 Help for TGMTRI

The input dataset must be a triangles dataset, normally the output dataset
from the program TRIGRID.

The output dataset will be a halfword image dataset. The value at each pixel
corresponds to the record (line) number in the input file that would be used
to compute the old pixel location that maps to this point.

NL is the number of lines in the output image.  It should be the number of
lines in the rectified image that will be created by TGEOM2.

NS is the number of samples in the output image.  It should be the number of
samples in the rectified image that will be created by TGEOM2.