Abstract
In order to improve the observation capability in one of the most active volcanic areas in the world, Mt. Etna, we developed a processing method to use the surveillance cameras for a quasi real-time mapping of syn-eruptive processes. Following an evaluation of the current performance of the Etna permanent ground NEtwork of Thermal and Visible Sensors (Etna_NETVIS), its possible implementation and optimization was investigated to determine the locations of additional observation sites to be rapidly set up during emergencies. A tool was then devised to process time series of ground-acquired images and extract a coherent multi-temporal dataset of georeferenced map. The processed datasets can be used to extract 2D features such as evolution maps of active lava flows. The tool was validated on ad-hoc test fields and then adopted to map the evolution of two recent lava flows. The achievable accuracy (about three times the original pixel size) and the short processing time makes the tool suitable for rapidly assessing lava flow evolutions, especially in the case of recurrent eruptions, such as those of the 2011–2015 Etna activity. The tool can be used both in standard monitoring activities and during emergency phases (eventually improving the present network with additional mobile stations) when it is mandatory to carry out a quasi-real-time mapping to support civil protection actions. The developed tool could be integrated in the control room of the Osservatorio Etneo, thus enabling the Etna_NETVIS for mapping purposes and not only for video surveillance.
Highlights
In volcanic areas, where it is often difficult to access the most critical zones to carry out direct surveys, digital photogrammetry techniques have remarkable potential for following the evolution of volcanic activity and monitoring deformation processes [1,2,3,4]
Digital photogrammetry processing is based on the application of matching procedures between overlapping images using autocorrelation algorithms capable of working at subpixel level [5]
The systematic acquisition of airborne photogrammetric datasets can be adopted for long-term volcano monitoring and hazard assessment [1,2]
Summary
In volcanic areas, where it is often difficult to access the most critical zones to carry out direct surveys, digital photogrammetry techniques have remarkable potential for following the evolution of volcanic activity and monitoring deformation processes [1,2,3,4]. Oblique digital images, frequently acquired by helicopter, can be processed, for example with the scientific tool Orthoview [7] that uses a straightforward photogrammetric approach to generate digital orthophotos. The processing, through photogrammetric software, of digital images taken from helicopter, light aircraft or ground can be used to extract DEMs from points identified in multiple photos. Oblique stereo-pair time-lapse imagery acquired on the ground can be processed by combining close-range photogrammetry and traditional stereo-matching software or by using a software based on structure-from-motion, to extract
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