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Estimating the 3-D flow rates of the Lowell Glacier using spaceborn InSAR Zhang, Xiangzhou Joe


Glacier motion data is very important for glaciology research, but traditional methods for collecting such data need to overcome staggering financial and logistical hurdles. During the period from July 1995 to May 1996, ERS-1/2 operated under Tandem Mission Mode with one satellite following the other one day apart. This gives a great opportunity to using Synthetic Aperture Radar (SAR) interferometry (InSAR) technology to measure the relative large displacement on the ground between the observation pair. Pioneer research work shows that this short time interval can maintain relatively high coherence for most glacier movement investigations. Some good results have been achieved to measure the velocity field of ice fields, ice streams and Alpine glaciers [1, 2, 3, 4]. In this study, the rationale and processing scheme of differential InSAR are discussed and examined first. Then 10 Tandem raw data sets (4 descending passes, 6 ascending passes) over the Lowell glacier at the boundary of B.C. and the Yukon, Canada, have been processed. 6 interferograms with enough coherence magnitude (3 ascending passes, 3 descending passes) have been generated. In concert with three different flow assumptions on the glacier movement direction, the line of sight (LOS) displacements along the glacier centreline measured from the ascending orbit and the descending orbit are converted into the 3-D velocity vectors. Our results show that the surface parallel assumption is more suitable for most part of the glacier. An overall accuracy around 4 cm/day rms has been achieved in measuring the surface motion of the Lowell Glacier. However, the 3-D projection model does not apply for the glaciers at all locations on this planet. The glacier has to be away from the critical regions caused by the projection geometry. Also, in order to achieve high estimation accuracy, the flow direction of the candidate glacier has be approximately aligned with the radar LOS. But with specifical satellite missions, this technique can provide a feasible method for monitoring the global glaciers and ice sheets in the future.

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