Abstract: The United States gradually released the 1"(about 30 m) SRTM DEM (Shuttle Radar Topography Mission Digital Elevation Model)data to global users in September 2014. To compare the difference between 1" and previously released 3"(about 90 m) SRTM DEM data on InSAR(Interferometric Synthetic Aperture Radar), interferograms are produced by using radar images from the European Space Agency's (ESA) Envisat and the influence of different DEM on the single interferogram and the average velocity of multiple interferograms covering the Pearl River Delta region analyzed. The results show that the difference between 1" and 3" DEM on the single interferogram is proportional to the length of the perpendicular baseline. For an interferometric pair with perpendicular baseline of 50 m, for example, the difference is distributed within ±4 mm, and 89% of which is within ±1 mm. Due to the random distribution of the perpendicular baselines for multiple interferograms in a track, the difference of the average rate obtained from all the interferograms is within ±4 mm/yr, and 90% of which is within ±1 mm/yr. Therefore, it is concluded that 1" and 3" SRTM DEM have no significant difference on InSAR deformation monitoring in the Pearl River Delta.

Key words: Interferometric Synthetic Aperture Radar (InSAR), Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM), Pearl River Delta, deformation monitoring