## 3 Results
According to the statistical results in Table 5, at an elevation of 5197.5100 m, the glacier movement speed by GB radar interfer  
Figure 8: The glacier movement speed map extracted by Sentinel-1 and the phase accumulation results of the sampling points at the glaciers termini measured by GB radar time-series interferometry: (**a**) Description of glacier movement speed map of Rongbuk Glacier and phase accumulation of sampling points of Rongbuk Glacier termini; (**b**) Description of glacier movement speed map of Yangbulake Glacier, etc., and phase accumulation of sampling points of Yangbulake Glacier termini. ometry measurement is 7.74 cm/day, while the result obtained by Sentinel-1 is 11 cm/day; at an elevation of 5130.7875 m, the glacier movement speed by GB radar interferometry measurement is 4.10 cm/day, while the result obtained by Sentinel-1 is 3 cm/day. The two results are generally consistent, indicating the feasibility of GB radar interferometry for measuring glacier movement speed. Further analysis shows that the accuracy of ground-based radar interferometry measurement reaches the sub-millimeter level, and the distance resolution can be calculated as 0.5 m based on the speed of light and bandwidth. However, the accuracy of satellite remote sensing data is centimeter level, and the spatial resolution is meter level, indicating that GB radar has better monitoring performance. For the phase accumulation map and fitting analysis of the sampling points at the glacier termini by GB radar interferometry measurement on the right side of Figure 8a,b, the determination coefficient \((R^{2})\) of the fitting results at the Rongbuk Glacier termini is 0.68 and the determination coefficient \((R^{2})\) of the fitting results at the Yangbulake Glacier termini is 0.99. The closer the coefficient is to 1, the better the fitting effect. The measured results in the monitoring of the termini of the Yangbulake Glacier are highly consistent with the fitting results, but there are significant differences in the analysis of Sentinel-1 data results. The GB radar measurement result is 198.96 cm/day, while the Sentinel-1 measurement result is 11 cm/day. Due to the melting season of glaciers during field measurements and the fact that the Yangbulake Glacier is a non debris-covered glacier, its movement speed is very fast. However, the revisit period of the Sentinel-1 radar satellite is relatively long, and the two interfered images differ by 12 days. In addition, the terrain in the study area is complex, and natural phenomena such as snowfall, melting, wind blown snow, avalanches, and cracks can cause changes in the scattering characteristics of the target. Therefore, the misalignment of the two SAR images often leads to some \"hollow values\" or speed mutation points in the speed map [51]. When the glacier moves too fast and exceeds the monitoring range of offset tracking technology, it is also difficult to monitor the glacier movement. On the other hand, GB radar uses second level sampling, with a total signal acquisition time of less than 1 min, which can obtain information on glacier movement changes better. This also indicates that GB radar interferometry measurement has better monitoring effects when the glacier movement speed is fast. In order to better analyze the satellite radar remote sensing results, coherence coefficient maps of Sentinel-1 InSAR data were extracted and statistically analyzed. The results are shown in Figure 9 and Table 6.  
Overall, from the coherence coefficient maps on the left side of Figure 9a,b, the coherence coefficients in the two regions are mostly low. From the statistical maps on the right side of Figure 9a,b, it can be seen that the coherence coefficient values of most pixels are less than 0.4. When the pixel value is about 0.2, the count of pixels is at the peak level, indicating that the number of pixels is the highest when the coherence coefficient is 0.2.