I don think so. You must do just algebraic sum: perhaps negative values are "filling" and positive are "excavation". It depends on which layer is subtracting.
The mask is for delimiting the area of interest only. ----------------- What I mean in Spanish if my English is bad: No creo que debas hacer eso. Sólo deberías hacer la suma algebraica: tal vez los valores negativos son "relleno" y los positivos son "excavación". Depende de qué capa está restando. La máscara es sólo para delimitar el área de interés. -------------------- Carlos 2013/3/5 Pedro Venâncio <[email protected]> > Hi Carlos, > > Thank you for your great tip! > > I was thinking... creating masks to separate the negative valuesfrom the > positive valuesof the raster 'Hight', I can get the excavation and > landfill volumes, right? > > > Thanks! > Pedro > > > > > > ----- Original Message ----- > From: Carlos Cerdán <[email protected]> > To: [email protected] > Cc: > Sent: Tuesday, March 5, 2013 11:16 PM > Subject: Re: [Qgis-user] Volume between two surfaces > > One idea: > > Use calculator on GRASS and do: > > Surface 1 - Surface 2 = Hight > > We have the heigth value on each cell, so now use r.sum: > > Volume = r.sum (of Hight) * side of pixel ^2 (if cells are squares) > > Of course, you must use a mask to boundary your area of interest > > Carlos Cerdán > > > El 05/03/13 17:49, Pedro Venâncio escribió: > > Hi all, > > > > Is there any way to calculate the volume between two surfaces (two DEM > rasters)? > > > > There are ways to calculate the volume between a surface and a > particular height value (GRASS r.volume or SAGA Grid Volume) but I can not > find how to calculate the volumes (landfill / excavation) between two DEM. > > > > Any tips? > > > > Thank you very much! > > > > Best regards, > > Pedro Venâncio > > > > _______________________________________________ > > Qgis-user mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/qgis-user > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > >
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