1,721,037 research outputs found
Il Territorio
No full textGuida del territorio e del patrimonio artistico del comune di Sellano (Perugia
Quantitative Geodiversity Index: GIS & spatial analysis for assessment and selection of geomorphosites
No full textThe research centered on geoconservation and geotourism stressed qualitative methods focusing on the definition, identification, study and development of geosites. Although the excellent results achieved by scientific international research, the topic of quantitative evaluation of geodiversity is still an open field.
To define a quantitative index of geodiversity is the next step required in order to quantify this parameter. Geographical Information Systems (GIS), Digital Elevation Models (DEM) and remote sensing imageries are the new instruments available to develop specific tools in order to obtain quantitative indexes.
The formula proposed in this abstract takes into account abiotic factors, contributing to the geodiversity definition, with intrinsic characteristics of spatial continuity (geological substrate, soil cover, land use) or spatial discontinuity (morphogenetic processes). Moreover the topographic parameter is strongly stressed out, modeled through the roughness or an index that measures how irregular an area is from a topographic point of view. The relevance of topography is a consequence of two points:
1. the roughness is strictly related to efficiency of geomorphological processes and generally is corresponding to a greater variability of the abiotic component.
2. The great availability of new DEMs with advanced characteristics of vertical accuracy and horizontal resolution. These models allow to manage the topographic attributes obtaining promising results and highlighting the energy relief role in the geodiversity comprehension.
The study area is the Umbria region (central Italy) and covers many lithological and morphological units, becoming an ideal representation of the conditions of geodiversity in central Italy.
The results of this approach could be not only an advance in the quantitative approach of geodiversity assessment but also a valid instrument for landscape management and geotourism and geoparks evaluation, promotion and management
La valutazione della pericolosità da uragano in ambiente GIS:il caso dell’uragano Dennis su Cuba
No full textNegli ultimi anni la valutazione della pericolosità degli eventi naturali quali gli uragani attraverso l’uso della tecnologia dei Sistemi Geografici Informatici (GIS), rappresenta un avanzamento nella ricerca per la comprensione di tali fenomeni. Nonostante i metodi presenti in letteratura per valutare la pericolosità siano riconducibili soprattutto a tre differenti approcci (euristico-qualitativo, statisticoquantitativo e deterministico) numerose sono le domande ancora irrisolte. In particolare per comprendere quale sia il processo principale che sta alla base di un sistema così complesso, in cui componenti tra loro eterogenee sono legate le une alle altre da molteplici interazioni, è necessario disporre di una gran quantità di informazioni sui diversi tipi di pericolosità (LANDSEA et alii, 2004). Visti gli effetti degli uragani sia lungo le aree di costa che nell’entroterra, un elemento chiave risulta essere lo studio delle caratteristiche fisiche degli eventi correlati: onde anomale, venti particolarmente intensi e inondazioni. L’analisi mediante GIS dei parametri che li caratterizzano, quali la topografia, la batimetria, la velocità dei venti, il reticolo idrografico, è stata d’ausilio nella valutazione delle relazioni intercorrenti per effettuare una zonazione del territorio in aree omogenee secondo il grado di suscettibilità all’evento
Detecting alluvial fans using quantitative roughness characterization and fuzzy logic analysis using the Shuttle Radar Topography mission data
No full textIn Geomorphology the landforms delineation and delimitation are based on traditional techniques which is usually achieved by two different approaches: semantic and geometric. The semantic approach involves interpreting aerial photographs as well as using field knowledge to map the possible landforms extent. The geometric approach involves inferring the probability of extension on related properties through observations of topographic attributes like slope, elevation and curvature. This report, based on a similarity geometric model, uses quantitative roughness characterization and fuzzy logic analysis to map alluvial fans. We choose to work in the Italian central Apennine intermountain basins because of much human activities could mask this kind of landforms and because the timing of alluvial deposition is tied to land surface instabilities caused by regional climate changes. The main aim of the research is to understand where they form and where they extent in an effort to develop a new approach using the backscatter roughness parameters and primary attributes (elevation and curvature) derived from the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM). Moreover, this study helps to provide a benchmark against which future alluvial fans detection using roughness and fuzzy logic analysis can be evaluated, meaning that sophisticated coupling of geomorphic and remote sensing processes can be attempted in order to test for feedbacks between geomorphic processes and topography
Strategy to delineate potentially affected areas by Hurricane using a GIS approach: the Dennis event on Cuba island
No full textIn the last decade, statistical modelling of hurricane in potentially affected areas by GIS has become a major topic of research. Despite some basic approach based on the «weight of evidence», some unsolved questions are still under discussion. The disastrous effects of hurricanes on coastal communities are well known, and there is a need to better understand the causes and the hazards contributions of the different events related to hurricane like storm surge, floods and high winds. The selected approach is to determine a sudden onset zoning from a set of available attributes that are considered to govern the hazard while we examine the influence of each individual events that produce the final hazard along the coastline (WHITE & WANG, 2003). To assess the coastal susceptibility, important parameters include topography, bathymetry, storm track into coast proximity, and river network. For all this parameters, key attributes based on SRTM and bathymetry data are the river network delineation based on the Strahler methodology, the slope data, and coastline bathymetry identification. Complementary data for the final model includes existing density rain dataset, elevation datasets for selected coastal drainage basins, and existing hurricane tracks inventories together with hurricane structure model (different buffers related to the Saffir-Simpson scale in a GIS environment). The hazard results was then overlaid with population data in the overall assessment of coastal hazard risk. The approach, which made use of a number of available global data sets, was then validated on a regional basis using past experience on hurricane frequency study over an area that covers both developed and developing countries in the Caribbean region. The final output of the research was the development of a multi-hazard model that incorporate statistical decision-science techniques
Criteria for the elaboration of susceptibility maps for DGSD phenomena in central Italy.
No full textIn this research we analyze the overall requirement and use of parameters derived from geomorphic technique for Deep-seated Gravitational Slope Deformation (DGSD) susceptibility assessment in the Central Apennine (Umbria-Marche area - Italy). The geometric parameters characterizing the topography affected by DGSD are investigated by remote sensing data. In particular, Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) improved with Landsat ETM+ imageries are used to detect the topography signature representative of DGSD susceptibility. Landsat ETM+ data are processed with Spectral Mixing Analysis (SMA). The topographic DGSD signature is determined by different topographic parameters such as slope, relief, aspect and curvature which can be used as a DGSD index degree. To characterize important physical properties of the aforesaid signature, the linear mixing model between the dark surface endmember and both the substrate and vegetation endmembers was used. That model highlights the extent to which shadowing and non-reflective surfaces, combined with illuminated substrate and vegetation at sub-pixel scale, can modulate spectrally mixed ETM+ reflectances in a ridge topography within the DGSD signature. The final results indicate that when incorporated with optical SMA of the Landsat ETM+, the SRTM analysis should improve the capacity for mapping and identifying DGSD in specific landscapes
Detecting alluvial fans using quantitative roughness characterization and fuzzy logic analysis
No full textThis research, based on a similarity geometric model, uses quantitative roughness characterization and fuzzy logic analysis to map alluvial fans. We choose to work in the Italian central Apennine intermountain basins because much human activities could mask this kind of landforms and because the timing of alluvial deposition is tied to land surface instabilities caused by regional climate changes. The main aim of the research is to understand where they form and where they extent in an effort to develop a new approach using the backscatter roughness parameters and primary attributes (elevation and curvature) derived from the SRTM DEM. Moreover, this study helps to provide a benchmark against which future alluvial fans detection using roughness and fuzzy logic analysis can be evaluated, meaning that sophisticated coupling of geomorphic and remote sensing processes can be attempted, in order to test for feedbacks between geomorphic processes and topography
A 3D approach using Landstat images types and SRTM data to map Deep Seated Gravitational Slope Deformations (DSGSD).
No full textIdentification and mapping of landforms in geomorphology are based on geological and geomorphological survey and interpretation of topographic maps and aerial photos. Considerable enhancement for morphometric interpretation can be obtained through generation of a synthetic stereo pair, by means of the integration of spectral data with Digital Elevation Model derived by Shuttle Radar Topography Mission (SRTM). The global coverage and moderate spatial resolution (30 m) offered by Landsat 7 are a necessary complement to the SRTM imagery and the combined use of both systems would allow for greater accuracy than either could provide independently. Although earlier applications of previous Landsat missions have met with mixed success for landscape mapping, more sophisticated methodologies combined with advances in the ETM+ sensor will facilitate the mapping objective. In addition to an improved signal/noise ratio in the multispectral bands and higher spatial resolution (60 m) in the thermal band, the ETM+ sensor also provides a panchromatic band with 15 m spatial resolution. The multispectral and panchromatic bands can be combined using pan-sharpening algorithms to provide a more detailed view. Classification algorithms that accommodate spectral heterogeneity provide a way to discriminate heterogeneous built environments from more homogeneous natural environments. Spectral Mixture Analysis (SMA) classifies individual mixed pixels according to the distribution of spectrally pure end member fractions and provides a tool for discrimination and classification.
Some landforms, as DSGSD (Deep Seated Gravitational Seated Deformations) have a well defined evidences recognizable by topographic surface observation and deriving from their morphologic characterization. Trenches, double ridges and counterslopes are the superficial evidences of the mass movements scarp edges. Sagging, cambering and a widespread landsliding are the evidences of compressional stress deformation in the lower part of the slope.
Our methodology is direct towards the automatic analysis of the geomorphologic parameters which characterize the arrangement of the DSGSD (such as the slope, the curvature and the relief), starting from a DEM. The method classifies the landscape into geographic areas as function of complex interdependent parameters rather than a single parameters.
To understand the behaviour of all the parameters pertaining to DSGSD and to process their automatic reduction in morphological unit we use the three bands (147) of Landsat ETM. Then we used PCA analysis in order to map them for separating homogenous areas into these morphological unit. In this case PCA helps us to groups the DSGSD areas bringing out the similarity in the morphometric characteristics.
The multitemporal spectral mixture analysis will yield continuous change fraction maps as well as thematic classifications for each date. A class change analysis will yield the discrete change classifications. The result of the mapping will be continuous end member fraction maps and thematic classification maps for 1990 and 2000 as well as continuous and discrete change maps. These can be used to constrain the spatial distribution and type of DSGSD regions. On the basis of these spectra, we anticipate that it will be possible to determine which classes can and cannot be distinguished in the Landsat imagery
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