I am trying to find ways to calculate a volume with :
- 1 base DEM resolution 1m
- 1 elevation DEM resolution 1m
First method: Using the extension volume calculation tool as follows. The result seems correct 22484 m3.
Second method: I wanted to do the calculations by hand from a DEM representing the difference between elevation and base DEM. So in raster calculator :
then in theory, I have to multiply number_of_pixel by surface_of_pixel by sum_of_pixel_value
With zonal statistics algorithm, I have number of pixels and the sum of their values (?).
Here is the point : 56495 * 1 * 22503,27 = too many m3.
It seems obvious that I do something wrong in the second way but can't figure it out.
raster surface volume
or the SAGA toolraster volume
?