The comparison of 4721 high accuracy DGPS reference points collected from different locations at Egypt and at different altitude/slopes confirm the absolute vertical accuracy of Copernicus DEM to be < 4 meters.
The average of the vertical shift about -0.19m with 1.44 Standard Deviation, and the slope of this points ranges from 0 to 32 degree and the points elevation ranges from 6 to 781 meters above sea level.