[GRASSLIST:5106] value of Null in CELL rasters

[Thomas Dewez]

Dear all,

I am exporting my raster coverages to GMT to draw pretty maps (so 
I find). For CELL files (ie results of a r.clump in my case) the 
commands do work well. Note the -ZTLh option in xyz2grd 
necessary to such integer grid.

R=`g.region -p | awk '{if($1 ~ "west") west=$2} {if($1 ~ "east") 
east=$2} {if($1 ~ "north") north=$2} {if($1 ~ "south") 
south=$2}END{printf "-R%s/%s/%s/%s",west,east,south,north}'`
echo $R

r.out.bin input=$inGRASS output=- | xyz2grd $R -ZTLh -F -I10 -
Dm/m/m/1/0/=/= -G$outGMT

As it happens the result of r.clump contains loads of Null values. 
The switch -N"number" explicitly defines what Null values are. But 
what is it in case of integer rasters? Is it different for other types of 
raster (ie floating points)?

Cheers,

Thomas Dewez
PhD Student
Dept Geography & Earth Sciences
Brunel University (West London)
Uxbridge UB8 3PH, Mddx
United Kingdom

Phone: +44-(0)1895-203215
Fax:     +44-(0)1895-203217

e-mail: thomas.dewez at brunel.ac.uk