## 4 Results
### Comparison of DInSAR Displacement with Feature Tracking and DEM Differencing
#### 4.1.2 Grison Sites  
The Grison sites show various settings, which have a strong variability in their suitability for DInSAR analysis, whereas the Nair site is less suited due to its north-facing direction (Figure 5a,b), which reduces the detectability of displacement in both acquisition orbits. The Gianda Grischa site is strongly affected by layover and shadow effects, especially in the upper parts of the rock glacier beneath the rock faces (Figure 5d,e). On the other hand, Muragl has better suitability except for the upper parts of the rock glacier, which is also north-facing (Figure 5g,h). The Davains site is well-suited except for the top parts in the east located directly beneath the rock face (Figure 5k,l). When comparing the East-West component derived from FT with the results from DInSAR, we see effects similar to those in the Kaiserbergtal valley site. The yearly DInSAR displacement makes up again roughly about one third of the movement detected by FT (Figure 5c,f,i,m). This represents the fraction of the year with snow-free or stable snow cover conditions. Hence, we applied a scaling of 3 on the DInSAR displacement values for the statistical assessment. The Pearson correlation coefficient ranges from 0.45 for the Nair site to 0.70 for the Davains site. RMSE is lowest for the Gianda Grischa site at 5 cm, and highest for the Davains site at 26.5 cm. The SD ranges from 20 cm at Gianda Grischa to 50 cm at Davains. Further, we can again  
Figure 4: Comparison of annual horizontal East-West displacement and elevation change of the Kaiserbergtal study site. The left column shows (**a**) E-W displacement from Feature Tracking and (**c**) elevation change from DEM differencing based on the UAV imagery. The middle column shows the respective (**b**) E-W displacement and (**d**) the elevation change derived from DInSAR. The white outline shows the area covered by the UAV reference dataset. (**e**) The scatterplot describes the distribution of the measurements; contour lines show kernel density estimates (levels: 0.3; 0.5; 0.7; 0.9). Background maps: ©Google Satellite.  
identify an increasing underestimation for larger displacement rates. At Gianda Grischa and Nair, this effect starts to occur already at about 0.4 m FT displacement (Figure 5c,f). At Muragl, the effect is visible for absolute values of higher than 0.3 m and becomes more dominant from 0.6 m onwards, showing a constantly increasing underestimation with higher displacement rates (Figure 5i). At Davains, only a slight underestimation occurs at absolute values below 0.9 m and then an abrupt offset of about 0.15 m in DInSAR displacement is visible for values of higher than 1.0 m (Figure 5m). This offset then remains stable for higher displacement values.  
Figure 5: Comparison of annual horizontal E-W displacement of the study sites in Grison: (**a–c**) Nair, (**d–f**) Gianda Grischa, (**g–i**) Muragl, (**j–l**) Davains. The left column shows result from Feature Tracking based on the orthophotos. The middle column shows the respective E-W displacement derived from DInSAR. The right column shows scatterplots of these two independent datasets with contour lines highlighting kernel density estimates (levels: 0.3; 0.5; 0.7; 0.9). The white outline in the maps (50 m buffer around rock glacier units) was used to exclude areas outside from analysis. Background maps: @wissstoppo.