GRASS text file format.

A GRASS text file (produced using the GRASS command r.out.ascii) has a small header, and then a string of ASCII pixel values, as follows;

north:     xxxxxx.xx
south:     xxxxxx.xx
east:       xxxxxx.xx
west:      xxxxxx.xx
rows:     r
cols:      c
xxxxxxxxxxxxxxx (pixel values, as integers)

Every GRASS layer read will be checked against the existing data set for consistency in shape, size and bounds.