Joint Monitoring Glacier Displacement of the Cuolangma Glacier Based on LuTan-1 and Sentinel-1A Imageries with SAR Offset Tracking

Objectives: Against the backdrop of global climate warming accelerating the melting of glaciers and snow, which in turn triggers geological disasters such as glacier debris flows and glacial lake outburst floods, monitoring glacier displacement using China's independently developed LuTan-1 (LT-1) satellite helps fill the gap in the currently limited research on this topic. Methods: We selected the Cuolangma Glacier in Tibet, China, as the experimental subject and conducted a comparative study of glacier displacement using offset tracking techniques with Sentinel-1A imagery and LT-1 imagery from 2022. Additionally, the Helmert variance component estimation method was applied to jointly process both datasets to calculate the glacier's three-dimensional deformation rate. Results: The results indicate that both the median window and mean window offset tracking methods improve the accuracy of offset calculations. It also shows that LT-1 provides higher offset calculation accuracy and spatial resolution compared to Sentinel-1A. Experimental results further reveal that the maximum cumulative displacements of the Cuolangma Glacier in 2022 along the azimuth and line-of-sight (LOS) directions were 21.45 m and -7.61 m, respectively. The jointly processed three-dimensional deformation rate results show that, from April to September 2022, the maximum deformation rates of the glacier in the east-west, north-south, and vertical directions were -0.125 m/d, 0.147 m/d, and -0.134 m/d, respectively. The displacement of the glacier's upper part primarily occurred towards the east and north, showing a gradual retreat trend; the displacement in the middle part primarily occurred towards the west and north, with glacier material gradually accumulating; and the displacement in the lower part primarily occurred towards the east and north, also showing a gradual retreat trend. Conclusions: The LT-1 satellite data from China, using offset tracking technology, can effectively monitor glacier movement and shows superior performance compared to Sentinel-1A. The joint processing method provides a valuable reference for three-dimensional glacier monitoring in the high-altitude regions of Tibet.