Resumen de Inferring glacier surface velocity and digital elevation models from sythetic aperture radar images
Pablo Sánchez Gámez, Francisco José Navarro Valero 
The use of Synthetic Aperture Radar (SAR) for inferring glacier surface velocities and digital elevation models (DEMs) has been performed since the advent of this technology at the beginning of the 1990s. The potential of SAR interferometry to infer surface deformations is hindered by the loss of coherence due to the glacier surface changes. The limitation produced by rapid glacier flow and its effect on SAR coherence can be overcome with the use of offset-tracking techniques. The main aim of this contribution is to give an insight on the use of the intensity feature tracking technique for estimating the glacier velocity field. This procedure will be applied over two different platforms, the already decommissioned ALOS PALSAR-1 satellite and the latest ESA Sentinel-1 platform. An analysis of the seasonality of the inferred ice velocities will also be made to illustrate some of the possibilities provided by this technology.
We investigate the impact of the satellite image resolution on the inferred ice velocity field, provided that PALSAR-1 offered a 5 m resolution in its fine mode versus its Sentinel-1 counterpart, whose resolution goes down to 3 and 22 m in range and azimuth directions, respectively, when using its interferometric wide mode (Stripmap resolution is only supported in emergency management scenarios). The lowest resolution of Sentinel-1, which at first sight could be seen as a downside, could be overridden by ESA’s satellite improved temporal resolution which is three times larger. Furthermore, an innovative iterative procedure, based on the use of the interferometric approach and a reference DEM from the area, will be used to obtain a finer DEM for King George Island from TanDEM-X SAR images. In this case, the SAR loss of coherence is overcome by the satellites’ common acquisition of the same area which limits the contribution of temporal decorrelation. The information on ice surface velocity fields and DEM, together with in situ measured GPR data, will be used afterwards, in a further study, to infer ice thickness and ice discharge from the South Shetland Islands, to the northwestern of the Antarctic Peninsula. Keywords: Synthetic Aperture Radar, Digital Elevation Models, Ice motion, Interferometric SAR, Radar offset-tracking, South Shetland Islands.
