Use of historical flight for landslide monitoring
Javier Cardenal 1, Jorge Delgado 1, Emilio Mata 1, Alberto González 2
and Ignacio Olague 2
1 Department of Ingenieria Cartografica, Geodesica y Fotogrametria
University of Jaen. Campus Las Lagunillas, s/n. 23071-Jaen (Spain)
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2 Department of Earth Sciences and Condensed Matter Physics.
University of Cantabria. Avenida de Los Castros, s/n. 39005-Santander (Spain)
Landslides are one of the most frequent deformations in the shallow layers of the Earth. These deformations have very important social and economic consequences being one of the more hazardous natural risks. For this reason, the landslides knowledge and modelling are actually a very interesting research line in order to establish the susceptibility of a certain zone to be affected by one of these processes. Digital photogrammetry can be used for monitoring landslides since allows for high accuracy calculation of spatial coordinates of points in unstable slopes and its surroundings. Present aerial digital photogrammetric techniques have shown to be effective into the susceptibility and hazard analysis of the land instability processes at moderate costs. The Digital Elevation Models (DEM), obtained by means of digital photogrammetry, have a high accuracy and precision and improve the results of mass movements’ susceptibility models. This methodology has been applied in an area localized in the internal valleys of the Cantabrian Range (Northern Spain). An interesting aspect of the project has been the data processing of available historical flights in order to increase the historical record of present information. Thus a total of 5 flights on the study areas were available from 1958 to 2001, with scales between 1:33.000 and 1:15.000 and with color and panchromatic films. The final quality of available originals (obtaining negatives in good condition for scanning was really difficult) and the available information ( there were cases with no information about the geometric camera parameters) have taken to select two flights: a 1:20.000 scale panchromatic flown at 1970 and a 1:15.000 scale color flown at 1988. DEM accuracy was better than 1.5 m and 2 m in XY and Z, respectively. In these cases comparison with present photogrammetric flights (larger 1:10000 and 1:5000 ad hoc flights for the project) has allowed the monitoring of the temporal evolution of landslide crowns (expressed as annual rates of displacements). Other historical flights have also been processed to check out the extent of the metric capabilities of old aerial paper print photographs when an important lack of information about the flight project exists. All flights have been processed with a digital photogrammetric workstation (DPW) running under Leica Photogrammetry SuiteTM (LPS).
Keywords: digital photogrammetry, historical flights, deformation monitoring, landslides
In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português