Digital Elevation Model (DEM) is crucial to a wide range of surveying and civil engineering applications
worldwide. Some of the DEMs such as ASTER, SRTM1 and SRTM3 are freely available open source products. In order to evaluate the three DEMs, the contribution of EGM96 are removed and all DEMs heights
are becoming ellipsoidal height. This step was done to avoid the errors occurred due to EGM96. 601
points of observed ellipsoidal heights compared with the three DEMs, the results show that the SRTM1
is the most accurate one, that produces mean height difference and standard deviations equal 2.89
and ±8.65 m respectively. In order to increase the accuracy of SRTM1 in EGYPT, a precise Global
Geopotential Model (GGM) is needed to convert the SRTM1 ellipsoidal height to orthometric height, so
that, we quantify the precision of most-recent released GGM (five models). The results show that, the
GECO model is the best fit global models over Egypt, which produces a standard deviation of geoid undulation differences equals ±0.42 m over observed 17 HARN GPS/leveling stations. To confirm an enhanced
DEM in EGYPT, the two orthometric height models (SRTM1 ellipsoidal height + EGM96) and (SRTM1
ellipsoidal height + GECO) are assessment with 17 GPS/leveling stations and 112 orthometric height stations, the results show that the estimated height differences between the SRTM1 before improvements
and the enhanced model are at rate of 0.44 m and 0.06 m respectively. |
