*3.1.6 Data integration*

In September 2015, time-lapse photography and terrestrial radar campaigns were conducted simultaneously to measure the Planpincieux Glacier surface kinematics. The actual three-dimensional surface kinematics was obtained by coupling DIC and TRI results. **Figure 10** reports the mean daily velocity map, where the colour represents the velocity module and the arrows indicate direction and versus. The 3D displacement can be obtained only in the areas visible by both the sensors. In the right lobe, the displacement vectors are not uniformly parallel to the surface, because the seracs move downstream as a single body and the ice is subjected to internal deformation. This result is not trivial, as the most common approach to estimate 3D displacement is to project the single movement components along the local slope obtained from the DEM, but this assumption might be misleading in specific cases.

The permanent monitoring system of the Whymper Serac is composed of RTS and time-lapse imagery. In July 2019, the data of the two sensors were integrated and represented in an informative bulletin [54, 55], shown in **Figure 11**. Such integration allows evaluating the versus and direction of the principal movement (with the RTS data) and the distribution of the strain rates (with the DIC results).

#### **Figure 10.**

*Velocity field of the surface kinematics of the lower Planpincieux Glacier obtained with the integration of DIC and TRI measurements. Colours and arrows represent velocity module and direction respectively. Modified from Dematteis et al. [6].*

**Figure 11.**

*Data integration of DIC and RTS measurements. The image depicts the spatially distributed daily deformation of the Whymper Serac front (coloured dots) and the surface displacement direction measured by the TRS in correspondence with the prism P3-2017. The right plot reports the displacement trend provided by the RTS.*
