Traditional geomorphological analyses was mainly supported by photointerpretation methodologies allowing a stereoscopic vision of the territory, or to low-resolution satellite images analysis for morphostructural studies at small scale, in which the 3D is negligible. Here a quantitative analysis is proposed based on digital photogrammetric methodologies, which resulted crucial in landslide studies. The whole middle and upper parts of Susa Valley, Italian Western Alps are interested by large slope instabilities. In the study area an active geomatic approach is applied, based on the multitemporal DEM (Digital Elevation Model) differential analysis. Apparently the Sauze of Oulx area doesn't have present-day superficial deformation of particular importance or dangerousness for buildings. Nevertheless it could be interesting to monitor the slow but constant movements in time, due to compressive and stretching forces that have interested the deposits of the ancient phenomenon, the "paleo-landslide". In this case the analyses will be focused on the main driving cause, that is, on the large slope instability that characterizes the area. An evaluation procedure, based on digital photogrammetry stereoplotting techniques, has been developed in two phases: 1) orthoprojection of images, in order to assess the cartographic scale of applicability; 2) analysis for specific geometric stereoplotting devoted to landslide vertical movement measurement. Two stereoscopic series of frames have been used for the production of the ground digital models (DEM) referred to years 1964 and 2000. The two DEM, have been compared elaborating a matricial subtraction (later - first) through a special selfdeveloped IDL procedure (Interactive Data Language). In order to underline just the meaningful vertical movements (those that correspond within the esteemed tolerance) a precautionary threshold has been applied equal to +/- 4m from bibliography (tolerance = 2σ; Kraus, 1994) . A vertical movement map has been produced. The results have been confirmed by measures on the same study area, through land and satellite interferometric echniques. The new high resolution sensors allow the acquisition of stereoscopic couples of images for the enhancement of 3D landslide analysis: validation tests are in progress to check the 3D data derived from these new satellite images.
Il ruolo della geomatica nell’analisi e nella rappresentazione di forme complesse legate alla dinamica dei versanti: il caso di Sauze d’Oulx (Valle di Susa)
PEROTTI, Luigi;GIARDINO, Marco;BORGOGNO MONDINO, ENRICO CORRADO
2008-01-01
Abstract
Traditional geomorphological analyses was mainly supported by photointerpretation methodologies allowing a stereoscopic vision of the territory, or to low-resolution satellite images analysis for morphostructural studies at small scale, in which the 3D is negligible. Here a quantitative analysis is proposed based on digital photogrammetric methodologies, which resulted crucial in landslide studies. The whole middle and upper parts of Susa Valley, Italian Western Alps are interested by large slope instabilities. In the study area an active geomatic approach is applied, based on the multitemporal DEM (Digital Elevation Model) differential analysis. Apparently the Sauze of Oulx area doesn't have present-day superficial deformation of particular importance or dangerousness for buildings. Nevertheless it could be interesting to monitor the slow but constant movements in time, due to compressive and stretching forces that have interested the deposits of the ancient phenomenon, the "paleo-landslide". In this case the analyses will be focused on the main driving cause, that is, on the large slope instability that characterizes the area. An evaluation procedure, based on digital photogrammetry stereoplotting techniques, has been developed in two phases: 1) orthoprojection of images, in order to assess the cartographic scale of applicability; 2) analysis for specific geometric stereoplotting devoted to landslide vertical movement measurement. Two stereoscopic series of frames have been used for the production of the ground digital models (DEM) referred to years 1964 and 2000. The two DEM, have been compared elaborating a matricial subtraction (later - first) through a special selfdeveloped IDL procedure (Interactive Data Language). In order to underline just the meaningful vertical movements (those that correspond within the esteemed tolerance) a precautionary threshold has been applied equal to +/- 4m from bibliography (tolerance = 2σ; Kraus, 1994) . A vertical movement map has been produced. The results have been confirmed by measures on the same study area, through land and satellite interferometric echniques. The new high resolution sensors allow the acquisition of stereoscopic couples of images for the enhancement of 3D landslide analysis: validation tests are in progress to check the 3D data derived from these new satellite images.
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