DESCRIPTION
File map is used as reference file.
Cells in the mask are marked as "mask out" if the corresponding cell in
map contains a value in the range specified with maskvalues.
Before a new 3D-mask can be created the exisitng mask has to be removed
with g.remove.
SEE ALSO
g.remove
AUTHORS
Roman Waupotitsch, Michael Shapiro,
Helena Mitasova, Bill Brown, Lubos Mitas,
Jaro Hofierka