Evaluation of the damages caused by seismic events: First tests on supporting traditional multispectral classification with DSM

Seismic damages, as a roof entirely collapsed on the ground, are very difficult to be found using only multispectral classification algorithms. The availability of high resolution stereopairs from satellite disclose new possible fields of application to estimate changes and transformations of areas following catastrophic events. Combining both techniques it is obviously possible only when stereoscopic and multispectral images are available. In this case, as for all monitoring studies, it is necessary to compare the present situation to the pre-seismic one. The pre-seismic situation can be advantageously studied by classic photogrammetric techniques based on aerial frames, that are available in archives managed by photogrammetric companies and local government agencies. But it is also possible to extract the pre-seismic morphology from digital maps, containing the three-dimensional characteristics of the buildings. The present research tries to: a) improve the digital surface model extracted from Ikonos satellite images covering an area of central Italy (Foligno, Umbria), through a pre-treatment of images and a manual editing b) study the best DSM models to improve the detection of height difference, mainly in urban areas, and evaluate the results of the classification of land cover as further data to detect changes in building shape. DSM obtained by three-dimensional maps have been compared with DSM extracted directly from aerial stereo-pairs using different approaches. In the area under study a seismic event happened in September of the '97 causing relevant damages to different urbanized centres of the area

Automatic three-dimensional features extraction: The case study of L'Aquila for collapse identification after April 06, 2009 earthquake

This paper illustrates an innovative methodology for post-earthquake collapsed building recognition, based on satellite-image classification methodologies and height variation information. Together, the techniques create a robust classification that seems to yield good results in this application field. In the first part of this study, two different feature extraction methodologies were compared, based respectively on pixel-based and object-oriented approaches. Then the classification results of the most accurate classification methodology, obtained on an eight band WorldView-2 monoscopic image, were completed with height variation information before and after the event. The height difference is calculated, comparing a photogrammetric DSM, obtained using a photogrammetric rigorous orbital model on some EROS-B 0.7 metre across-track stereopairs with a 'roof model' before the earthquake

Use of aerial multispectral images for spatial analysis of flooded riverbed-alluvial plain systems: the case study of the Paglia River (central Italy)

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

Three-dimensional multispectral classification and its application to early seismic damage assessment

The recent seismic events that have affected different areas of the planet point out the need to respond quickly to emergencies caused by these events; for this reason a semi-automatic method was experimented which would provide information concerning the damaged buildings in the study area through satellite images. In September 1997 an earthquake hit the study area, causing significant damage to a number of towns and villages in the area. This research attempts to: a) improve the digital surface model extracted from Ikonos satellite images covering an area of central Italy (Foligno, Umbria), through the pre-processing of raw images and manual editing b) study the best DSM models to improve the detection of height differences, mainly in urban areas, and evaluate the results of the land cover classification as further data for detecting changes in building distribution. DSM obtained by three-dimensional maps have been compared with DSM extracted directly from aerial stereo pairs using different approaches. The innovative aspect of the experiment is that of wanting to evaluate whether the combined use of multispectral classification techniques and altimetric aspects taken from high-resolution satellite images can make the recognition of changes to buildings affected by the earthquake more robust. The same methodology can be used also for updating existing medium-scale maps; in this case as well, the comparison of data regarding the same area but for different periods is important

Coastline Detection Using High Resolution Multispectral Satellite Images

In the last 50 years the inhabitants of the 19 municipalities along the Abruzzo coast have doubled, and a stronger impact of the activities connected with the tourism has been experienced. The area, naturally exposed to the effects of changes of the sea level, has been interested by a dramatic increase of erosion, due to the reduction of the solid transport from rivers to the sea, as a consequence of extensive works carried out on the watersheds to mitigate extreme rainfall and consequent flooding. The availability of data acquired by different sensors on the last few decades might be useful to assess overall accretion/erosion trend of coastline, whereas combination of different observations taken in a restricted timeframe may provide interesting inputs for detailed studies (e.g. about the local impact of coastline protection works). In the present paper is proposed a methodology for the coastline identification from WorldView-2 images, available in 8 spectral bands, with 0.5 m of spatial resolution for panchromatic images and 1.8 m for the multispectral channels. In particular, a pixel based multispectral classification was used to identify various types of land cover. The 8 bands allow to get good results both in the classification process and with NDVI, NDWI, SAM, FM algorithms, for the identification of various land cover and in particular to separate dry sand from wet sand. Interesting results were obtained testing an algorithm that evaluates the relative depth of the water using the “coastal blue” band. Better results can surely be obtained by using elevation data (geoid models and digital terrain models) integrated with radiometric information. Very interesting is the comparison of the estimated coastline with such methodology and a topographic map of same area. This comparison highlights the changes in the study area. The possible applications of the proposed techniques are many, such as map updates, but also coastal change monitoring

Automatic shoreline detection from eight-band VHR satellite imagery

Coastal erosion, which is naturally present in many areas of the world, can be significantly increased by factors such as the reduced transport of sediments as a result of hydraulic works carried out to minimize flooding. Erosion has a significant impact on both marine ecosystems and human activities; for this reason, several international projects have been developed to study monitoring techniques and propose operational methodologies. The increasing number of available high-resolution satellite platforms (i.e., Copernicus Sentinel) and algorithms to treat them allows the study of original approaches for the monitoring of the land in general and for the study of the coastline in particular. The present project aims to define a methodology for identifying the instantaneous shoreline, through images acquired from the WorldView 2 satellite, on eight spectral bands, with a geometric resolution of 0.5mfor the panchromatic image and 1.8mfor the multispectral one. A pixel-based classification methodology is used to identify the various types of land cover and to make combinations between the eight available bands. The experiments were carried out on a coastal area with contrasting morphologies. The eight bands in which the images are taken produce good results both in the classification process and in the combination of the bands, through the algorithms of normalized difference vegetation index (NDVI), normalized difference water index (NDWI), spectral angle mapper (SAM), and matched filtering (MF), with regard to the identification of the various soil coverings and, in particular, the separation line between dry and wet sand. In addition, the real applicability of an algorithm that extracts bathymetry in shallow water using the "coastal blue" band was tested. These data refer to the instantaneous shoreline and could be corrected in the future with morphological and tidal data of the coastal areas under study

Geometrical Characterization of Hazelnut Trees in an Intensive Orchard by an Unmanned Aerial Vehicle (UAV) for Precision Agriculture Applications

Knowledge of tree size is of great importance for the precision management of a hazelnut orchard. In fact, it has been shown that site-specific crop management allows for the best possible management and efficiency of the use of inputs. Generally, measurements of tree parameters are carried out using manual techniques that are time-consuming, labor-intensive and not very precise. The aim of this study was to propose, evaluate and validate a simple and innovative procedure using images acquired by an unmanned aerial vehicle (UAV) for canopy characterization in an intensive hazelnut orchard. The parameters considered were the radius (Rc), the height of the canopy (hc), the height of the tree (htree) and of the trunk (htrunk). Two different methods were used for the assessment of the canopy volume using the UAV images. The performance of the method was evaluated by comparing manual and UAV data using the Pearson correlation coefficient and root mean square error (RMSE). High correlation values were obtained for Rc, hc and htree while a very low correlation was obtained for htrunk. The method proposed for the volume calculation was promising

Ii deficit finanziario nell'ordinamento comunale

Nell'ambito del corso di lezioni dell'insegnamento di diritto degli enti locali, con riferimento all'argomento: ordinamento finanziario e contabile, si è approfondito il tema della disciplina dell'indebitamento ed il suo rapporto con il principio di equilibrio del bilancio. Tra gli aspetti di maggiore interesse le procedure di riequilibrio finanziario e di dissesto