A relevant part of the Assisi urban area (central Italy), built up after 1950 and located outside of the ancient town center, is interested by a landslide characterized by a slow rate of movement, still causing important damages for an accumulation effect in time. For the monitoring of the landslide behaviour, the determination of the motion field and its evolution in time, a precision GNSS network has been established over the area since 1995, connecting by means of a baseline network the moving area with stable geologic formations. Further (1999), a leveling network has been added to improve the definition of the vertical component of the motion field and the density of controlled points. Surveys have been carried out until the actuality. Time series of coordinates and heights spanning along the observation period (1995 or 1999 to 2010) are hence available for the network points. The Assisi landslide area has also been investigated by means of InSAR: the data here presented derive from the analysis of Envisat data spanning in time from 2003 to 2010, thus with a 7-years overlapping with the GNSS and leveling surveys, which make possible a comparison. SAR data refer to scatter points which are numerous and well spread over the landslide area but almost never coinciding with GNSS and leveling markers. Moreover, the type of movements which can be put into evidence are different: along an assigned direction (LOS) from the SAR data, in 3 dimensions from GNSS, along the vertical direction from leveling. This paper presents a comparison of the InSAR results with the GNSS data, from which the LOS component has been derived. The comparison has been made for each GNSS marker with the surrounding SAR scatters, trying to take into account local topological effects when possible. A comparison between InSAR and leveling data requires a different approach, considering the different one-dimensional components of the movement, vertical for leveling and oblique (along the LOS) for InSAR.
InSAR, GNSS and leveling comparison on multi-annual series for the study of landslide surface deformation
G Fornaro;F Bovenga;
2012
Abstract
A relevant part of the Assisi urban area (central Italy), built up after 1950 and located outside of the ancient town center, is interested by a landslide characterized by a slow rate of movement, still causing important damages for an accumulation effect in time. For the monitoring of the landslide behaviour, the determination of the motion field and its evolution in time, a precision GNSS network has been established over the area since 1995, connecting by means of a baseline network the moving area with stable geologic formations. Further (1999), a leveling network has been added to improve the definition of the vertical component of the motion field and the density of controlled points. Surveys have been carried out until the actuality. Time series of coordinates and heights spanning along the observation period (1995 or 1999 to 2010) are hence available for the network points. The Assisi landslide area has also been investigated by means of InSAR: the data here presented derive from the analysis of Envisat data spanning in time from 2003 to 2010, thus with a 7-years overlapping with the GNSS and leveling surveys, which make possible a comparison. SAR data refer to scatter points which are numerous and well spread over the landslide area but almost never coinciding with GNSS and leveling markers. Moreover, the type of movements which can be put into evidence are different: along an assigned direction (LOS) from the SAR data, in 3 dimensions from GNSS, along the vertical direction from leveling. This paper presents a comparison of the InSAR results with the GNSS data, from which the LOS component has been derived. The comparison has been made for each GNSS marker with the surrounding SAR scatters, trying to take into account local topological effects when possible. A comparison between InSAR and leveling data requires a different approach, considering the different one-dimensional components of the movement, vertical for leveling and oblique (along the LOS) for InSAR.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.