Up-to-date digital elevation model (DEM) products are essential in many fields such as hazards mitigation and urban management.Airborne and low-earth-orbit (LEO) space-borne intefferometric synthetic aperture radar (InSAR) has been proven to be a valuable tool for DEM generation.However,given the limitations of cost and satellite repeat cycles,it is difficult to generate or update DEMs very frequently (e.g.,on a daily basis) for a very large area (e.g.,continental scale or greater).Geosynchronous synthetic aperture radar (GEOSAR) satellites fly in geostationary earth orbits,allowing them to observe the same ground area with a very short revisit time (daily or shorter).This offers great potential for the daily DEM generation that is desirable yet thus far impossible with space-borne sensors.In this work,we systematically analyze the quality of daily GEOSAR DEM.The results indicate that the accuracy of a daily GEOSAR DEM is generally much lower than what can be achieved with typical LEO synthetic aperture radar (SAR) sensors;therefore,it is important to develop techniques to mitigate the effects of errors in GEOSAR DEM generation.