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This paper assesses the accuracy of the SRTM v4.1 and ASTER GDEM v2 by comparing of sufficient number of ground control points (GCPs) with corresponding pixel values of DEMs heights for two locations in Egypt : Delta region(A) &West desert and Qena region (B). A new approach was developed for accuracy enhancement based on (Weight Estimation Regression models) ,with Topographic Position Index(TPI), Aspect, SRTM or ASTER DEM as independent variables and GCP as dependent values . Data were analyzed for each location separately and in combination ,using GIS and statistical software (SPSS). The results of this study showed that vertical Root Mean Square Errors (RMSE)for SRTM dataset range from 15.631 m in (A) to 7.868 m in (B). for ASTER dataset, RMSE ranges from 13.160 m in (A) to 12.357 m in (B) .For combined regions(A+B) :RMSE were 12.688 m and 12.7997 m for SRTM and ASTER datasets respectively . Concerning the accuracy enhancement of SRTM and ASTER DEMs , a significant improvement of Std. Error of Estimate (SEE) were detected in the two locations. For (A) SEE reduce from 13.584 to 9.502 for SRTM dataset and reduce from 12.538 to 9.101 for ASTER dataset. For (B) SEE reduced from 7.879 to 1.725 for SRTM dataset and from 11.006 to 5.769 for ASTER dataset . Also for combined region SEE reduced from 11.685 to 5.930 for SRTM dataset , and from 11.7624to 8.520 for ASTER dataset . The study also proved that TPI index for ASTER dataset give the best fit to the data for Weight Estimation procedure for better horizontal resolution (30m) . The results of assessments and the improvement approaches of SRTM and ASTER DEMs showed their level of suitability for many hydraulic , watershed, and environment applications.

ACCURACY ENHANCEMENT OF SRTM AND ASTER DEMS USING WEIGHT ESTIMATION REGRESSION MODEL