#  This macro is intended for initial use on contour quads being processed
#  into DEMs.

#   first single pixel holes are filled (so as not to form tiny polygons)
fill_holes

#   next 2 pixels are removed from each side of all lines
thin_lines 0 1

#   next all short spurs are deleted
#del_spurs 5
#   commented out by operator preference

#   last any remaining solid areas (cliffs) are opened up.
#open_solids
#   commented out by operator preference (on hi dpi scans it turns index
#   contours into canals.
