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This work presents an analysis of the applicability of synthetic aperture radar (SAR) interferometry to landslide monitoring. This analysis was carried out by using different interferometric approaches, different spaceborne SAR data (both in the C-band and in the X-band), and in situ global navigation satellite system (GNSS) measurements. In particular, we investigated both the reliability of displacement monitoring and the issues of the cross-comparison and validation of the interferometric synthetic aperture radar (InSAR) results. The work was focused on the slow-moving landslide that affects a relevant part of the urban area of the historical town of Assisi (Italy).A C-band ENVISAT advanced synthetic aperture radar (ENVISAT ASAR) dataset acquired between 2003 and 2010 was processed by using two different interferometric techniques, to allow cross-comparison of the obtained displacement maps. Good correspondence between the results was found, and a deeper analysis of the movement field was possible. Results were further compared to a set of GNSS measurements with a 7 year overlap with SAR data. A comparison was made for each GNSS marker with the surrounding SAR scatterers, trying to take into account local topological effects, when possible.Further, the high-resolution X-band acquired on both ascending and descending tracks by the COSMO-SkyMed (CSK) constellation was processed. The resultant displacement fields show good agreement with C-band and GNSS measurements and a sensible increase in the density of measurements.

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A wide area of the Assisi town, in Umbria (central Italy), is interested since its first edification (1950)(1951)(1952)(1953)(1954)(1955)(1956)(1957)(1958)(1959)(1960) by an extensive landslide. The rate of motion is very slow (around 1 cm/year), but the deformations accumulated for almost 60 years have produced considerable damage to many private and public buildings, including the civic hospital and an important Franciscan monastery. The University of Perugia established in 1995 a geodetic monitoring network over the Assisi landslide, connecting a number of control points inside the moving area to an external reference network with markers placed on stable geological formations. The monitoring has been based since the beginning on GPS satellite positioning with static observations, aiming to obtain a three-dimensional accuracy of about 1 cm level. From 2001 onwards, GPS+GLONASS receivers have been used for all measures, and more control points have been added in 2006, for a better description of the field of movements. Since 1999, a high precision levelling network has been set up over the landslide area, in order to improve the accuracy of the height component, increasing its monitoring sensitivity to a few millimetre level. During the years, observation campaigns have been repeatedly performed on both networks, accumulating a consistent and increasing quantity of data. Such database permits to carry out a series of analyses (coordinate time series, annual and accumulated displacement vectors, deformation velocity and deformation field) leading to a better comprehension of the landslide phenomenon and its evolution, helpful for the design of technical interventions. The Assisi landslideThe landslide under research interests a urban area of Assisi town, whose edification started in the years 1950-1960, as a planned expansion towards East of the historical town centre. The area is located on a slope (average inclination 21%) where no signs of motion where noticed at the time of the first building activity, albeit no in-depth analysis was performed. The urbanization of the area caused relevant changes to the flow regimen of the surface waters, deviating and in some cases closing existing ditches and streams. Around 1970, the first phenomena connected with an active landslide started to show, in the form of growing damage to buildings (initially attributed to local foundations failures), but also retaining walls, pipelines and street paving.From then on, the area was thoroughly investigated from a geological-geotechnical point of view, reaching the conclusion that it was interested by an active landslide with a surface extension of about 50 ha, and individuating an estimated perimeter of the moving area (Fig. 1). The landslide is of a gravitational type (translational creep), with a sliding surface located at an average depth of some tens of metres, with a maximum of about 60 m. The moving formation consists of a debris mass flowing over a stable bedrock composed of marl, sandstone and limestone. The morphology of...

The work in this paper illustrates an experimental application for geosciences by coupling new and low cost photogrammetric techniques: Gigapixel and Structure-from-Motion (SfM). Gigapixel photography is a digital image composed of billions of pixels (≥1000 megapixels) obtained from a conventional Digital single-lens reflex camera (DSLR), whereas the SfM technique obtains three-dimensional (3D) information from two-dimensional (2D) image sequences. The field test was carried out at the Ingelsberg slope (Bad Hofgastein, Austria), which hosts one of the most dangerous landslides in the Salzburg Land. The stereographic analysis carried out on the preliminary 3D model, integrated with Ground Based Synthetic Aperture Radar Interferometry (GBInSAR) data, allowed us to obtain the main fractures and discontinuities of the unstable rock mass.

ABSTRACT:The Tempio della Consolazione in Todi (16 th cent.) has always been one of the most significant symbols of the Umbrian landscape. Since the first times after its completion (1606) the structure has exhibited evidences of instability, due to foundation subsiding and/or seismic activity. Structural and geotechnical countermeasures have been undertaken on the Tempio and its surroundings from the 17 th century until recent times. Until now a truly satisfactory analysis of the overall deformation and attitude of the building has not been performed, since the existing surveys record the overhangs of the pillars, the crack pattern or the subsidence over limited time spans. Describing the attitude of the whole church is in fact a complex operation due to the architectural character of the building, consisting of four apses (three polygonal and one semicircular) covered with half domes, which surround the central area with the large dome. The present research aims to fill the gap of knowledge with a global study based on geomatic techniques for an accurate 3D reconstruction of geometry and attitude, integrated with a historical research on damage and interventions and a geotechnical analysis. The geomatic survey results from the integration of different techniques: GPS-GNSS for global georeferencing, laser scanning and digital photogrammetry for an accurate 3D reconstruction, high precision total station and geometric leveling for a direct survey of deformations and cracks, and for the alignment of the laser scans. The above analysis allowed to assess the dynamics of the cracks occurred in the last 25 years by a comparison with a previous survey. From the photographic colour associated to the point cloud was also possible to map the damp patches showing on the domes intrados, mapping their evolution over the last years.

Image processing and classification techniques are widely used for land use definition. They can also provide interesting applications in fluvial geomorphology, for outlining morpho-sedimentary features (bars, channels, banks and floodplain) at various temporal stages, in order to monitor the evolution of river systems. Frequent monitoring is especially important for streams, in terms of flood risk in urban areas. This study shows how techniques of supervised analysis can be applied to river systems, also under particular conditions, like after flood events (when large portions of riverbed and alluvial plain are covered with mud). The procedure starts from the classical photogrammetric techniques, based on multispectral classification, and goes on with post processing operations of pixel aggregation and shadow treatment. The classification also uses the elevation information provided by Digital Surface Model produced by photogrammetry. This paper introduces a new technique of remote sensing in fluvial areas that allows for both the identification and classification of the fluvial features in a post flooding condition. Application of the procedure over time permits the evolution of the fluvial dynamics to be monitored in an accurate and inexpensive way, particularly for flood event conditions which lead to major changes in the dynamics of riverbeds.

A large part of the archaeological remains still to be discovered and excavated are not in remote and depopulated areas of the earth but are often beneath urban centres that have buried them with centuries of debris and later constructions. Excavating in these contexts is much more complex than digging in rural or sparsely inhabited areas because of the constraints imposed by existing buildings and infrastructure. It should also be considered that within an urbanised area, any archaeological remains are concentrated in the subsoil of the historic centre, which is, therefore, often surmounted by buildings that are more recent than the remains but historical as well, and thus, of considerable value and vulnerability. For this reason, an archaeological excavation in an urban area must be preceded by a real feasibility study, where the potential risks for the structures above are minimised and accurately quantified. In many situations, as in the case under study, the discovery of a small segment of a structure is the only clue to reconstruct the development of the remaining part still to be excavated, which may stretch tens or hundreds of metres away from the measurable part. As a consequence, an error of a few centimetres in the survey of the excavated part can lead to errors of metres in estimating the positions of the far parts still to be excavated, and this, in many cases, as in the one under study, must absolutely be avoided. In practice, high-precision geomatic surveys, in support of the archaeological and historical interpretation of the observable structures, will help to establish the exact locations to possibly continue the excavations, helping the accurate planning of the excavation itself. Here, we have shown how the various techniques, compared to each other, have made it possible to reconstruct the location of a short stretch (less than 7 m) of the Emperor Augustus’ Sundial, the only currently visible evidence of a scientific instrument of imposing dimensions (tens of metres in length and height) that served to define some of the characteristics of the calendar that we still use today. The portion of the sundial currently observable, according to the most reliable hypotheses, is located approximately at one end of a structure and extends for several tens of metres. The accurate positioning of the observable parts in a geodetic reference system will enable to identify with certainty the possible areas in which excavation may continue and will also allow to accurately reconstruct the principle of operation of the sundial through an approach that could be defined as “reverse engineering” of the scientific instrument itself. The aim of this work is to study and thus define the combination and integration of existing geomatic techniques for this specific field of application.