## 4 Results and Discussion
### Shisper Glacier (Pakistan), PlanetScope DOVE  
The study area is located in the north flank of the Hunza Valley in the Central Karakoram. The Shisper glacier covers \(\sim\)53.7 km\({}^{2}\) at an elevation ranging between \(\sim\)2500 and 4500 m a.s.l. It has gained the attention of the scientific community and disaster response agencies due to a recent surge [38]. In 2018, the glacier surged beyond the confluence with the outlet stream of the Mochwar glacier. The blockage resulted in the creation of a lake, which then drained causing a GLOF (Glacial Lake Outbreak Flood) and has recently begun reforming [38]. The melt water from the two glaciers feeds hydropower plants in the Hunza valley and is a major source of fresh water for agriculture. Glacier-related hazards threaten both the town of Hassanabad and the Karakoram Highway, the only paved road crossing the Karakorum (Figure 11) [38; 39; 40]. Here, we show the potential of CubSat data to monitor such glaciers, which are not easily accessible to field observation, and assess their potential impact on power generation, water resources and infrastructure. Figure 9: (**a**) Shaded DEM of the Mørenci Mine are computed using SGM in the image space from tri-stereo SkySat images acquired on 1 January 2019; (**b**) Example of sub-scenes covering the area. (**c**) Profile along the transect (AA’) extracted from image space DEM and object space DEM. Figure 10: (**a**) Elevation changes over the Morecni Mine area computed from the difference of 2016 3 DEP LiDAR and January 2019 SkySat DEM; (**b**) Histogram of the elevation difference over stable terrain (panel (**a**) blue box); (**c**) Elevation profiles from SkySat and LiDAR DEMs; (**d**) Elevation difference profile. Profiles are extracted along transect AA’ indicated in panel (**a**). Figure 11: The test site Shisper Glacier, Karakoram, Pakistan. (**a**) Subset of Sentinel 2 true color ortho-image (TCI) over the study area captured on 16 March 2019. Randolf Glacier Inventory [41] outline of both glaciers are shown in red. Location of the ice-dammed lake is shown in light blue. Rivers are denoted in dark blue and Hassanabad village is outlined in green. (**b,c**) Histogram distribution  
corresponding to the percentage of overlapping images within image pairs in the dataset of 2017 (**d**) and 2019 (**e**). (**d**) Outlines of PlanetScope scenes over the study area between 9 September and 20 September 2017. (**e**) Outlines of PlanetScope scenes over the study area between 1 August and 13 August 2019. (**f**,**g**) Number of image overlap during 2017 (**f**) and 2019 (**g**). We used multi-date L1B DOVE-C PlanetScope data to extract two DEMs in 2017 and 2019 in order to compute the elevation difference caused by the glacier surge. The data set consists of 16 DOVE-C images acquired in three days in September 2017 before the surge, and 14 DOVE-C images acquired in 4 days in August 2019 after the surge (Figure 11d-e for a plot of the extent of different overpasses of PlanetScope images). Tables 16 and 17 in Appendix B lists the acquisition parameters of the 2017 and 2019 scenes, respectively. Cloud-free images and pairs with more than 20% of overlap were selected to perform the RFM refinement Figure 11b-c contains a plot of the overlapping histogram between different image pairs). Additionally, a DEM computed from WorldView-2 (WV-2) and GeoEye-1 (GE-1) collections acquired on 5 July 2019 and on 9 September 2019 respectively is used for comparison with our 2019 PlanetScope DEM (Appendix B). The DOVE-C PlanetScope data were used to generate DEMs in the object space with no ground control points. SIFT was used to extract and match tie points between the different image pairs. Then, the refinement was performed using the COSI-Corr-RFM package following the procedure described above. The re-projection error after the RFMs refinement is \(\sim\)0.38 pix and \(\sim\)0.35 pix with 2017 and 2019 PlanetScope data, respectively. Given the nominal GSD of these data, it corresponds to \(\sim\)1 m on the ground.