PSI - Issue 84

Erica Cernuto et al. / Procedia Structural Integrity 84 (2026) 1167–1174

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adopted by Casagli et al. (2009). Both methods showed limitations related to outliers caused by vegetation, whose coherence is affected by wind and seasonal changes. A finer grid was therefore preferred to minimise these effects. Once the grid was defined, a synthetic PS was computed at the centroid of each cell for both geometries (Figs. 3b,c). This value corresponds to the average LOS displacement of all PS within the cell over the full set of acquisition dates. Since the two acquisitions are not simultaneous, post-processing was applied to align the datasets, considering only the common time interval (06/01/2018–22/12/2022) and applying temporal interpolation to fill missing dates. Only cells containing synthetic PS in both geometries were retained, generating combined time series with LOS values from ascending and descending acquisitions (Fig. 3d). The combined LOS measurements were then used to estimate the actual displacement components by integrating the approaches proposed by Brouwer et al. (2021) and Farneti et al. (2023), suitably modified for the present case study. In the global reference system (E, N, V), the actual displacement d is estimated from the measured LOS displacement d LOS (Fig. 4a). To obtain a more meaningful representation of the actual motion, a local reference system (L, T, V) was adopted (Fig. 4b), fixed to the deformation phenomenon and with the T-axis aligned with the main movement direction derived from numerical modelling.

a

b

Fig. 4. (a) global reference system (N, E, V); (b) local reference system fixed to the deformation phenomenon (L, T, V) (adapted from Cernuto et al. 2025).

Using the local reference system, d LOS can be expressed as a linear combination of the actual displacement components d L , d T , and d V . Since only two independent LOS measurements (ascending and descending) are available, the system is underdetermined: = (1) where: d LOS ={ d A d D } , = [ sin sin ( +ɸ ′ ) sin cos ( +ɸ ′ ) cos sin sin ( +ɸ ′ ) sin cos ( +ɸ ′ ) cos ] , = { } To solve the system, displacements parallel to contour lines were assumed negligible (d L =0) consistently with the expected behaviour of gravitational landslides, where motion predominantly follows the direction of maximum slope (T-axis). Under this assumption, the system becomes determined and allows the estimation of the transverse and vertical displacement components: ̂ = −1 (2) where B is obtained from A by removing the column associated with the longitudinal component. Further details on the formulation and implementation of the decomposition procedure are provided in Cernuto et al. (2025).