[GRASS-user] extract by attribute from a dem

[Martin Landa]

Hi,

2007/11/21, nishith datta <nkdiitd2002 at gmail.com>:
> 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

r.mapcalc 'new=if(slopeoriginal <= 20, slopeoriginal, null())'

?

Martin

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-- 
Martin Landa <landa.martin at gmail.com> * http://gama.fsv.cvut.cz/~landa *