While comparing the DEMs of relatively small area raster (1) obtained of UAV data and (2) EU-DEM elevation model, I spotted around 30 meter difference in elevation between them.
Since no GCP was used while harvesting data and I know that commercial grade UAV GPS chips are not able to deliver accurate Z values, I checked my findings via elevationfinder.com which gave same results as EU-DEM.
To correct the data, I've established Z values difference for points which are easiest to identify on both rasters and recalculated it using Raster Calculator. I am not sure however whether this is the proper way to do it. Can somebody confirm or suggest other, more scientific and reliable approach?