I have the DEM of a defined region that has been split into sub-DEM with a resolution of 1 km x 1 km. When I merge the sub-DEM to create a single DEM (Raster -> Miscellaneous -> Merge), the overall result is quite satisfactory, but for some reason, when I compare the original altitude to the merged altitude, there are differences in some regions. I also realized that the tool transforms regions containing nodata into 0.
The profiles in the following figure was obtained using the Profile plugin (red: original DEM, blue: merged DEM).
Is there an explanation for this?
I realized that when I create a virtual raster from DEM, and then save it in GeoTiff format, I get the original DEM.
My question is therefore: besides the ease of use, is there any advantage to using the Merge tool instead of the virtual raster?