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Ground filtering and vegetation mapping using multi-return terrestrial laser scanning / Francesco Pirotti in ISPRS Journal of photogrammetry and remote sensing, vol 76 (February 2013)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 76 (February 2013) . - pp 56 - 63 Titre : Ground filtering and vegetation mapping using multi-return terrestrial laser scanning Type de document : Article/Communication Auteurs : Francesco Pirotti, Auteur ; A. Guarnieri, Auteur ; Antonio Vettore, Auteur Année de publication : 2013 Article en page(s) : pp 56 - 63 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] carte de la végétation [Termes IGN] classification dirigée [Termes IGN] densité de la végétation [Termes IGN] densité des points [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] filtrage de points [Termes IGN] hauteur de la végétation [Termes IGN] modèle numérique de surface [Termes IGN] modèle numérique de terrain [Termes IGN] télémétrie laser terrestre Résumé : (Auteur) Discriminating laser scanner data points belonging to ground from points above-ground (vegetation or buildings) is a key issue in research. Methods for filtering points into ground and non-ground classes have been widely studied mostly on datasets derived from airborne laser scanners, less so for terrestrial laser scanners. Recent developments in terrestrial laser sensors (longer ranges, faster acquisition and multiple return echoes) has aroused greater interest for surface modelling applications. The downside of TLS is that a typical dataset has high variability in point density, with evident side-effects on processing methods and CPU-time. In this work we use a scan dataset from a sensor which returns multiple target echoes, in this case providing more than 70 million points on our study site. The area presents low, medium and high vegetation, undergrowth with varying density, as well as bare ground with varying morphology (i.e. very steep slopes as well as flat areas). We test an integrated work-flow for defining a terrain and surface model (DTM and DSM) and successively for extracting information on vegetation density and height distribution on such a complex environment. Attention was given to efficiency and speed of processing. The method consists on a first step which subsets the original points to define ground candidates by taking into account the ordinal return number and the amplitude. A custom progressive morphological filter (opening operation) is applied next, on ground candidate points using a multidimensional grid to account for the fallout in point density as a function of distance from scanner. Vegetation density mapping over the area is then estimated using a weighted ratio of point counts in the tri-dimensional space over each cell. The overall result is a pipeline for processing TLS points clouds with minimal user interaction, producing a Digital Terrain Model (DTM), a Digital Surface Model (DSM), a vegetation density map and a derived Canopy Height Model (CHM). These products are of high importance for many applications ranging from forestry to hydrology and geomorphology. Numéro de notice : A2013-092 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2012.08.003 En ligne : https://doi.org/10.1016/j.isprsjprs.2012.08.003 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32230 [article]

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Collaborative web-GIS design: a case study for road risk analysis and monitoring / Francesco Pirotti in Transactions in GIS, vol 15 n° 2 (April 2011)  

Public [article]  inTransactions in GIS > vol 15 n° 2 (April 2011) . - pp 213 - 226 Titre : Collaborative web-GIS design: a case study for road risk analysis and monitoring Type de document : Article/Communication Auteurs : Francesco Pirotti, Auteur ; A. Guarnieri, Auteur ; Antonio Vettore, Auteur Année de publication : 2011 Article en page(s) : pp 213 - 226 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique web [Termes IGN] accident de la route [Termes IGN] approche participative [Termes IGN] portail [Termes IGN] requête spatiale [Termes IGN] sécurité routière [Termes IGN] service web géographique [Termes IGN] SQL [Termes IGN] temps réel [Termes IGN] trafic routier [Termes IGN] WebSIG [Termes IGN] zone à risque Résumé : (Auteur) This article presents a methodology for designing a WebGIS framework intended for automatically analyzing spatial data and updating statistics of interest with new information inserted daily by multiple users via a Web portal. A practical example is used on vehicle accident data for assessing risk in specific road segments. Two main blocks integrated together will be described: the collaborative block and the data-analysis block. The former gives end-users computer-aided tools to view, insert, modify and manage data related to accidents and traffic monitoring sensors, whereas the latter is developed to automatically analyze the accident data coming from user's collaboration. Because different agencies can survey accident sites, a collaborative environment is necessary – and a Web-based solution is ideal – for permitting multi-user access and data insertion. A centralized approach to process the data in real time is described in all its components. Server-side Structured Query Language functions optimize performance by using dedicated libraries for spatial processing and re-structuring the attributes associated with elements which are consequently re-classified for correct color-scaling. The end-product is a system that provides a seamless integration of front-end tools for user collaboration and back-end tools to update accident risk statistics in real time and provide them to stakeholders. Numéro de notice : A2011-106 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1467-9671.2011.01248.x Date de publication en ligne : 04/04/2011 En ligne : https://doi.org/10.1111/j.1467-9671.2011.01248.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30886 [article]