When it comes to NULL value and different extents of rasters I find it extremely cumbersome to use QGIS raster calculator. As far as I am aware there is no way to operate with NaN/Null value. So no matter what you do NaN/NULL in any input become NULL in output.
As far as I am aware you can't do anything like:
(raster1 is NULL)*raster2+(raster1 is not NULL)*raster1
I have similar issue with extents of raster. I have one raster of large extent and second covering only small part of it. I need to update null/zero values of large extent raster to values in small extent raster. If I do calculation below everything off of small extent becomes NULL/Nan.
(largeraster = 0)*smallraster + (largeraster != 0)*largeraster
Is there any way to be able to operate with NULL value in raster calculator? Is there any way to not trash all values in areas where all rasters do not overlap?