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Offset Tracking procedure applied to the Viedma Glacier, Patagonian Andes, Argentina
Conferencia; Alexander von Humboldt International Conference. Natural Disasters, Global Change, and the Preservation of World Heritage Sites.; 2012
Offset Tracking is used to estimate the movement of glacier surface from two SAR acquisitions in slant-range and azimuth directions. This alternative for estimating glacier motion is useful when the Differential SAR Interferometry (DInSAR) is limited by coherence loss, e.g. the case of rapid flow and/or large time intervals of acquisition between the two SAR images. Application of this indirect technique is relatively faster and more economical comparing to other traditional methods for glacier monitoring. This fact is relevant for climate studies in the Patagonian Andes where main glaciers are remote with a very difficult access. Even this technique is well known worldwide, it has not been widely applied in Argentinean glaciers. Herein Offset tracking technique was applied to the Viedma Glacier (Santa Cruz, Argentina), one of the largest uncovered ice body in the South Patagonian Ice (SPI) which ice area reaches 945km2 ending its glacier tongue in the Viedma Lake. In this study, the Offset Tracking was conducted by pairs of COSMO-SKYMED data to estimate offset fields in the glacier. These satellite images were acquired from April-2012 to July-2012 in ascending and descending mode, while data time intervals between the pairs resulted 1, 16, and 32 days, respectively. The high spatial resolution dataset of these images (1.25 x 2.40 m) allows to determinate further details on the surface of this uncovered ice glacier. Besides obtained map of glacier displacement defines clearly areas or units with different flowing velocities. Faster displacements are determined in the glacier tongue, while minor displacements seem to be related to irregularities of topography constraining basal displacement coinciding with changes in glacier direction (curves). Still previous research on behavior of the Viedma glacier front has been conducted by other authors (Svkarca et al., 1995; Aniya et al., 1999), our findings could not be contrasted as they lack on measurement of ice glacier mass velocity. Error estimation on glacier surface displacement could result from co-registration of images and the time lag between each pairs of images. To obtaining more precision, the spurious component of motion has to be measured on fixed target outside of the glacier and subtracted.