Satellite survey enhances knowledge of Tuscan landslides   Its combination of mountainous landscapes, high rainfall and uncontrolled urbanisation of unstable land makes Italy one of the countries most affected by landslide hazards. An average of 54 victims per year were claimed by landslides during the last half century.   The Arno River Basin is an area with a high landslide hazard. ESA's SLAM project involves making use of Earth Observation data to better quantify the risks of landslides arising within the Arno River Basin. Highlighted in this image are the Casalino and Carbonile areas, where close-up studies have been carried out.   The so-called 'Permanent Scatterer' method of Synthetic Aperture Radar Interferometry (InSAR) involves combining multiple radar images of the same location, using 'stable scatterers' such as rock outcrops or buildings to avoid signal decoherence and make measurements of millimetre-scale ground shifts occurring between acquisitions. Permanent-Scatterer InSAR is at the basis of the SLAM project in Italy, aimed at better quantifying landslide hazard and employing a decade's worth of archived satellite data. Here permanent scatterer measurements are overlaid on a Spot 5 image and wrapped on a digital elevation model.   Recorded landslides occurring in the Arno River Basin shown in red, overlaid on a digital elevation model of the region.   Permanent Scatterer distribution over Casalino area (Poggibonsi near Siena). Permanent Scatterers are produced from combinations of multiple radar images of the same area and yield information on millimetre-scale ground movements occurring between acquisitions. This technique is at the heart of the SLAM service in Italy.   Since the 1980s the Carbonile area close to Florence, has been subject to several landslides, which affected both crops and buildings. In this image Permanent Scatterer (PS) measured displacement rates and activity status of landslides are highlighted over the area. Red indicates still active landslides (i.e. having moved in the last few years, PS in these areas showing peaks of deformation, in red). Grey indicates dormant landslides that according to geological and geophysical evidence (PS) moved in less recent times (e.g the last two years within a decade). Green highlights inactive landslides (no longer moving, as confirmed also by PS which show almost no movement within a decade - in green). PS distribution and velocity enables areas at risk to be highlighted.   SLAM Landslide Susceptibility Map in the Arno Basin. This product has been realised through the integration of motion information (millimetric ground displacements resulting from the Permanent Scatterers InSAR technology) with thematic maps of land use, slope, geomorphology and more. The Landslide Susceptibility Map is used as input to geological hazard and risk mapping and is to be considered as an important tool for land use planning and environmental impact assessment.   The SLAM project shows how satellite monitoring can improve the accuracy of landslide hazard estimation, helping secure lives and property. SLAM activities are currently being carried out in Italy and also Switzerland, two of the European countries most susceptible to slope instability.   ERS in orbital configuration. ERS-1 and -2 have generated about 1.5 million SAR scenes, and upwards of 3500 scientists have published more than 30 000 scientific papers based on ERS data. Release date: 8 June 2005