## 4 Results
### Periglacial Ground Deformations  
We compared the ground velocity map obtained by the GPOD-SBAS and the VDA rock glaciers (RGs) inventory [76]. In general, despite the widespread lack of targets coverage associated with the rock glaciers, we found a fairly good correlation. Considering the ascending orbit, 759 inventoried RGs were observed within the track considered (Table 4); in this case, just the 16% present targets inside, and only 4% present more than ten targets. For the descending orbit, a total of 811 phenomena inventoried are included within the task considered, of which 8% present targets, and only 2% present more than ten targets.  
The mean deformation velocity maps obtained for both ascending and descending orbits of the Envisat processing results reveal a generally low coverage of the rock glaciers by the targets. Figure 10 shows the mean deformation velocity map detail for the descending orbit acquisition, reporting an example of an intact rock glacier and a relict one. The Petit Emilius (PE in Figure 10a) RG corresponds to the intact one and presents only one target within, with a LOS velocity of \(-0.8\) cm/year, while the Becca di Nona (BN in Figure 10a) RG corresponds to the relict one and presents more than ten targets within, with a mean LOS velocity of \(-0.5\) cm/year, for the entire observed period.  
For these two cases, the analysis of the ground deformation time series of the targets (Figure 10b) reveals a constant deformation rate, with a maximum displacement of \(-1.4\) cm for the observed period from September 2004 to October 2010. Analyzing the time series in detail, they seem to display a sort of acceleration in correspondence to the summer and the mid-autumn (e.g., summer 2009). It is worth noting that such phenomena present a seasonal fluctuation [68], where the highest velocities appear during the summer to early autumn months; looking at the results from year to year, comparing the late summer with respect to the early subsequent summer, a moderate acceleration can be observed.  
Finally, considering the rock glaciers included within each track (Table 4), we observed in general that the intact rock glaciers present the largest deformation, while, for the rock glaciers identified as relict, a modest displacement, a smaller deformation with respect to the intact ones, was disclosed. In Figure 11, we present the Clapey Gerbioz relict rock glacier example: in ascending orbit (Figure 11a), this RG presents mean LOS velocities from \(-1.1\) cm/year up to \(-0.26\) cm/year; in descending orbit (Figure 11b), a range from \(-0.7\) cm/year up to \(-0.3\) cm/year.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Rock Glaciers (from** & **Rock Glaciers** & **Rock Glaciers** & **Rock Glaciers** \\  & **Glaciers Inventory** & **(within the Track)** & **Covered by Targets** & **with \textgreater{}10 Targets** \\ \hline ENVISAT Ascending & & & & \\ ENVISAT Descending & 937 & 811 & 65 & 13 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Summary of the number of rock glaciers, inventoried in the Glacier Inventory, covered by targets generated by the GPOD-SBAS process.  
Figure 11: _Cont._  
Figure 10: (**a**) Mean deformation velocity map of the Becca de Nona (BN) and Petit Emilius (PE) rock glaciers in descending orbit; (**b**) time series corresponding to the targets signed by the **white** dots in the map.