1,721,032 research outputs found
Landslide susceptibility map refinement using PSInSAR data
Full text linkLandslide susceptibility maps (LSM) are commonly used by local authorities for land use management and planning activities, representing a valuable tool used to support decision makers in urban and infrastructural planning. The accuracy of a landslide susceptibility map is affected by false negative and false positive errors which can decrease the reliability of this useful product. In particular, false negative errors, are generally worse in terms of social and economic losses with respect to the losses associated with false positives. In this paper, we present a new technique to improve the accuracy of landslide susceptibility maps using Permanent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) data. The proposed approach uses two different data sets acquired in ascending and descending geometry. The PS velocity measured along the line of sight is re-projected into a new velocity along the steepest slope direction (VSlope). Integration between the LSM and the ground deformation velocity map along the slope was performed using an empirical contingency matrix, which takes into account the average VSlope and the susceptibility degree obtained using the Random Forests algorithm. The Results show that the susceptibility degree increased in 56.41 km2 of the study area. The combination of PSInSAR data and the landslide susceptibility map (LSM) improved the prediction reliability of slow moving landslides, which particularly affect urbanized areas. The use of this procedure can be easily applied in different areas where PSI data sets are available. This approach will help planning and decision-making authorities produce reliable landslide susceptibility maps, correcting some of the LSM errors
Persistent scatterer interferometry (psi) technique for landslide characterization and monitoring
Full text linkThe measurement of landslide superficial displacement often represents the most effective method for defining its behavior, allowing one to observe the relationship with triggering factors and to assess the effectiveness of the mitigation measures. Persistent Scatterer Interferometry (PSI) represents a powerful tool to measure landslide displacement, as it offers a synoptic view that can be repeated at different time intervals and at various scales. In many cases, PSI data are integrated with in situ monitoring instrumentation, since the joint use of satellite and ground-based data facilitates the geological interpretation of a landslide and allows a better understanding of landslide geometry and kinematics. In this work, PSI interferometry and conventional ground-based monitoring techniques have been used to characterize and to monitor the Santo Stefano d'Aveto landslide located in the Northern Apennines, Italy. This landslide can be defined as an earth rotational slide. PSI analysis has contributed to a more in-depth investigation of the phenomenon. In particular, PSI measurements have allowed better redefining of the boundaries of the landslide and the state of activity, while the time series analysis has permitted better understanding of the deformation pattern and its relation with the causes of the landslide itself. The integration of ground-based monitoring data and PSI data have provided sound results for landslide characterization. The punctual information deriving from inclinometers can help in defining the actual location of the sliding surface and the involved volumes, while the measuring of pore water pressure conditions or water table level can suggest a correlation between the deformation patterns and the triggering factors. © 2013 by the authors; licensee MDPI, Basel, Switzerland
How can landslide risk maps be validated? Potential solutions with open-source databases
Full text linkLandslides are a worldwide natural hazard that cause more damage and casualties than other hazards. Therefore, social and economic losses can be reduced through a landslide quantitative risk assessment (QRA). In the last two decades, many attempts of quantitative analysis on various scales have been performed; nevertheless, the major difficulty of QRA lies in how precise and reliable the assessment should have to be useful. For this reason, in this paper, we analyzed different freely available datasets and some products of previous research to assess the soundness of the outcomes performed by a recent QRA of slow-moving landslides in the Arno River basin (Central Italy). The validation process was carried out by comparing the abovementioned datasets and two components of the selected QRA (hazard and risk). The obtained results showed a robust correlation between most of the testing dataset and risk components, highlighting the accuracy of the selected QRA
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A Landslide Susceptibility Map of the Messina Province (Sicily, Italy)
No full textLandslide susceptibility is the likelihood of a landslide occurrence in an area, assessed on the basis of local terrain conditions and represents the degree to which an area can be affected by future slope failure. Landslide Susceptibility Maps (LSM) are essential for land-use strategies as tools to support land management decision making. The production of a LSM can be obtained by using different methods, often through Geographic Information Systems (GIS). In this work, available data (i.e. geological and land cover maps, DEM-derived products and the pre-existing landslide inventory) were used to produce the landslide susceptibility map of the Messina Province (Italy), after the emergency occurred in 2009-2010. A simple implementation of Random Forest developed in Matlab was used to produce the LSM by performing multivariate classification. Results highlight most of the Province is susceptible to landslides, especially the Nebrodi Mountains, where detailed analysis have been planned to perform mitigation actions
TXT-tool 2.039-3.1: Satellite remote sensing techniques for landslides detection and mapping
No full textIn this work the application of remote sensing for landslide detection and mapping is described. Among Earth Observation (EO) techniques optical and radar images are very effective tools for these applications since very high spatial resolution obtained by optical systems (currently in the order of tens of centimeters) and by the launching of Synthetic Aperture Radar (SAR) sensors, purposely built for interferometric applications with revisiting times of few days. In this paper the potentiality of both satellite optical and radar data is explored in a selected case study, analyzing different slope instability processes at different scales. Thanks to them and to the support of existing bibliography, the main advantages and disadvantages are highlighted as well as some suggestions are proposed concerning the main fields of applications
From picture to movie: Twenty years of ground deformation recording over tuscany region (Italy) with satellite InSAR
Full text linkSynthetic Aperture Radar Interferometry (InSAR) techniques have been long exploited for detecting and mapping slow-moving ground surface displacements due to their millimeter accuracy, non-invasiveness and wide area coverage. A review on different applications of Persistent Scatterers InSAR approaches, proposed and applied over Tuscany region (Italy) across time, is here presented. The study area is characterized by both subsidence of alluvial plains and landslides on hilly and mountainous reliefs. Tuscany has a leading role in Italy in the field of interferometric applications: the first InSAR analyses, which date back to 2003, were performed at local basin scale, by exploiting various PSI-based approaches for risk mapping. The first InSAR applications at regional scale date back to 2009, relying on historical SAR archives of ERS and ENVISAT satellites for updating subsidence and landslide inventory maps at a certain temporal date. Nowadays, the availability of Sentinel-1 SAR data with a regular and systematic 6-days acquisitions plan, allows near-real time monitoring of deformative scenario at regional scale rather than solely mapping of geo-hydrological phenomena. Most recent innovative InSAR applications over Tuscany region scan the territory, exploiting the regular repeat pass of Sentinel-1, and promptly highlight the sites affected by the highest ground movements with high temporal frequency. Such approaches permit us to pass from a static ‘picture’ of regional slope instability to a weekly updated ‘movie’ with improved detail, useful for civil protection practices. These last ongoing works significantly enhance the value of multi-temporal InSAR approaches for investigating and managing geo-hazards over the Region
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