Evaluating the Effect of External DEMs on the Accuracy of InSAR DEM Generation

In recent years, the production of digital elevation models (DEMs) by using the interferometric synthetic aperture radar (InSAR) technique has become more useful compared to traditional methods. When DEM production is carried out by using this technique, an external DEM is used in the image processing steps. In this study, new DEMs were produced from an interferometric pair of TerraSAR-X images by using SRTM, ALOSW3D, TANDEM-X and STEREO DEMs with spatial resolutions of 90 m, 30 m, 12 m and 5 m, respectively. In addition, in situ measurements were carried out to collect control points and the accuracy of the obtained products was analyzed. The accuracy of the products obtained by using root mean square error, standard deviation and correlation coefficients were compared. The results obtained in this study demonstrated the effect of external DEMs in the DEM production stage with InSAR pairs and how accuracy increases with better external DEMs. In addition, the effect of the external DEM quality used was shown in the results. It was determined that provided the STEREO DEM reached the highest accuracy with the root mean square error value of 1.52 m. Also, analyzes were made according to different zones. According to the results, it was observed that the statistical errors increased in areas where the slope was steeper. While the RMSE of the rolling zone is 1.17 m, rugged zone is 2.33 m. The analysis results of the other DEMs from high to low quality were TANDEM-X, ALOSW3D and SRTM, respectively. It is thought that the results of this study can help to produce data with the required sensitivity in DEM production.