I would like to compare the elevation and volume of three DEMs. When I export the original DEMs in TIFF format the elevation values change. I do not use compression or any other kind of data transformation. It makes me wonder what the real elevation values are.
My second question is that I have calculated the volume difference of my DEMs (not the TIFF versions but the original) and it says that there is an increase in total volume between the DEMs. It is nearly impossible, since these are glacier surfaces that are known to decline in this area (and in most parts of the World). It is unlikely that there is a snow bias and my DEMs are in the same coordinate system and all clipped to the same vector shape.
Any idea what could have gone wrong?