抄録
This study demonstrates effectiveness of a global digital elevation model (GDEM) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data to detect surface displacements over ice sheet and ice streams in polar region by applying the DEM to SAR interferograms. Two interferograms were produced from two sets of interferometric pair data in 2007 and 2008 acquired by the Phased Array Type L-band Synthetic Aperture Radar (PALSAR) boarded on the Advanced Land Observing Satellite (ALOS) over an Antarctic ice sheet in the northern part of Enderby Land. The GDEM was used to remove topographic fringes and then we extract fringes induced by ice sheet surface displacements. By applying a differential interferogram procedure, displacement maps along the look vector were produced for the two observation time frames with a period of one repeat cycle (46 days), and clarified that the observed maximum displacements were about 1.94 m (corresponding to 15.4 m/yr) and 1.96 m (15.6 m/yr) during the recurrent period in 2007 and 2008, respectively. The topographic fringes were removed thoroughly over outcropped area in the scene by the usage of the GDEM, and the two displacement maps obtained after the removal of topographic fringes resembled each other. According to the error of the ASTER GDEM over snow and ice area, the influences on the displacement estimations were approximately ±1.5 cm (B⊥=−413 m) and ±1.8 cm (B⊥=−468 m) at the range center for the displacement maps in 2007 and in 2008, respectively. Moreover we produced a differential map between the displacement maps at the two time frames, and found the stability of ice sheet movements over the study area because the complicated displacement pattern such as concentric oval patterns associated with an ice sheet movement was disappeared in the differential map. This means that the GDEM is significant in applying it to SAR interferometric analysis.
