VALIDATION OF ETOPO5U IN THE HELLENIC AREA

Mean 5' x 5' heights and depths from ETOPO5U (Earth Topography at 5' s pacing Updated) Digital Terrain Model (DTM) were compared with corresp onding quantities of a local DTM in the test area [38-degrees less-tha n-or-equal-to phi less-than-or-equal-to 40-degrees, 21-degrees less-th an-or-equal-to lambda less-than-or-equal-to 240]. From this comparison a shift of ETOPO5U with respect to the local DTM in the longitudinal direction equal to 5 min was found after applying an efficient fast Fo urier transform (FFT) technique. Furthermore, sparse mean height diffe rences larger than 1,000 m were observed between ETOPO5U and the local DTM due rather to errors of ETOPO5U. The effect of these errors on gr avity and height anomalies was computed in a subregion. of the area un der consideration.