[GRASS-user] extract by attribute from a dem

[nishith datta]

hi all,
I have downloaded usgs srtm data from the esdi site in geoTiff format.
I next loaded it in grass and then created a slope map from it.
It shows values are in range from 0 to 86.0636.
next I used r.mapcalc with the expression
        r.mapcalc new=if( slopeoriginal<= 20)
to findout all areas which have less than 20 degrees of slope . It returned
nothing.
I tried with all values between 20 and 90 , no output ?!?!? atleast values
>=87 should have made a copy of the old
dem into the new . Isn't it ?
can someone help me out.
nishith
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