Abstract
The areas characterized by dynamic and rapid morphological changes need accurate topography information with frequent updates, especially if these are populated and involve infrastructures. This is particularly true in active volcanic areas such as Mount (Mt.) Etna, located in the northeastern portion of Sicily, Italy. The Mt. Etna volcano is periodically characterized by explosive and effusive eruptions and represents a potential hazard for several thousands of local people and hundreds of tourists present on the volcano itself. In this work, a high-resolution, high vertical accuracy digital surface model (DSM) of Mt. Etna was derived from Pleiades satellite data using the National Aeronautics and Space Administration (NASA) Ames Stereo Pipeline (ASP) tool set. We believe that this is the first time that the ASP using Pleiades imagery has been applied to Mt. Etna with sub-meter vertical root mean square error (RMSE) results. The model covers an area of about 400 km2 with a spatial resolution of 2 m and centers on the summit portion of the volcano. The model was validated by using a set of reference ground control points (GCP) obtaining a vertical RMSE of 0.78 m. The described procedure provides an avenue to obtain DSMs at high spatial resolution and elevation accuracy in a relatively short amount of processing time, making the procedure itself suitable to reproduce topographies often indispensable during the emergency management case of volcanic eruptions.
Highlights
Topography is the result of many Earth internal and external processes that interact and influence each other [1,2]
The validation vertical root mean square error (RMSE) decreased from 4.8 m to 0.78 m for the aligned more global matching (MGM) 2&3 digital surface model (DSM) model and the bias from +4.72 m to −0.52 m, respectively (Table 3)
The results indicate that (i) for the same stereo pair, there was no statistical significance between the vertical errors obtained using the local search window (LSW) or the MGM algorithms, the MGM algorithm always produced less noisy results with less data gaps; (ii) there was a marked statistical difference between the vertical errors obtained from different image combination pairs
Summary
Topography is the result of many Earth internal and external processes that interact and influence each other [1,2]. Several DEMs reproduce only limited portions of the volcano, generally those affected by a specific eruptive event [19,20,21] Often, these limited portions of topography are combined with older and larger area models of Mt. Etna to obtain what may be considered updated DEMs of the whole volcano. During the 2018 and 2019 volcanic activity, the areas affected by lava flows were surveyed by unmanned aerial vehicle (UAV) and data were processed using structure from motion (SfM). This allowed for the reconstruction of very high-resolution (up to 20 cm spatial resolution) digital surface models (DSMs) that displayed detailed lava flow morphologies [24]. The most recent model [23] covered the summit portion affected by the 2016 eruption, but no accuracy assessment was completed, and the reference system is not explicitly stated
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