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Using vertices of a triangular irregular network to calculate slope and aspect / Guanghui Hu in International journal of geographical information science IJGIS, vol 36 n° 2 (February 2022)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 36 n° 2 (February 2022) . - pp 382 - 404 Titre : Using vertices of a triangular irregular network to calculate slope and aspect Type de document : Article/Communication Auteurs : Guanghui Hu, Auteur ; Chun Wang, Auteur ; Sijin Li, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : pp 382 - 404 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique [Termes IGN] analyse comparative [Termes IGN] bassin hydrographique [Termes IGN] géomorphologie [Termes IGN] grille [Termes IGN] loess [Termes IGN] maillage [Termes IGN] méthode de Monte-Carlo [Termes IGN] modèle numérique de surface [Termes IGN] noeud [Termes IGN] pente [Termes IGN] point d'appui [Termes IGN] Triangulated Irregular Network Résumé : (auteur) Terrain derivative calculations from triangulated irregular network (TIN)-based digital elevation models (DEMs) have been extensively explored in geomorphometry. However, most calculation methods focus on the triangulation facets of TIN-based DEMs and ignore the vertices. In fact, these vertices are the original sampling points from the terrain surface and serve as the basis for triangulation. In this study, we argue that terrain derivative calculations using TIN-based DEMs should focus on the vertices. Employing examples with slope and aspect, we applied the TIN vertex-based method to a mathematical surface and a real topography using TIN-based DEMs with a range of sampling point densities. We performed a comparative analysis of the TIN vertex-based, TIN facet-based, and grid-based methods. Assessments on the mathematical surface showed that the TIN vertex-based method achieved the highest accuracy among the three methods. Error analysis for the real landform case indicated that the TIN vertex-based method performed slightly better than the grid-based method for slope calculation and slightly worse than the grid-based method for aspect calculation. Among the three methods, the TIN facet-based method was most sensitive to error. The TIN vertex-based method can provide a reference for the slope and aspect calculation based on point clouds. Numéro de notice : A2022-165 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2021.1933493 Date de publication en ligne : 01/07/2021 En ligne : https://doi.org/10.1080/13658816.2021.1933493 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99788 [article]

Estimating forest canopy cover in black locust (Robinia pseudoacacia L.) plantations on the loess plateau using random forest / Qingxia Zhao in Forests, vol 9 n° 10 (October 2018)  

Public [article]  inForests > vol 9 n° 10 (October 2018) Titre : Estimating forest canopy cover in black locust (Robinia pseudoacacia L.) plantations on the loess plateau using random forest Type de document : Article/Communication Auteurs : Qingxia Zhao, Auteur ; Fei Wang, Auteur ; Jun Zhao, Auteur ; Jingjing Zhou, Auteur ; et al., Auteur Année de publication : 2018 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] canopée [Termes IGN] Chine [Termes IGN] classification par forêts d'arbres décisionnels [Termes IGN] détection d'arbres [Termes IGN] Enhanced vegetation index [Termes IGN] image multibande [Termes IGN] image panchromatique [Termes IGN] loess [Termes IGN] matrice de co-occurrence [Termes IGN] plantation forestière [Termes IGN] régression [Termes IGN] Robinia pseudoacacia [Termes IGN] Soil Adjusted Vegetation Index Résumé : (Auteur) The forest canopy is the medium for energy and mass exchange between forest ecosystems and the atmosphere. Remote sensing techniques are more efficient and appropriate for estimating forest canopy cover (CC) than traditional methods, especially at large scales. In this study, we evaluated the CC of black locust plantations on the Loess Plateau using random forest (RF) regression models. The models were established using the relationships between digital hemispherical photograph (DHP) field data and variables that were calculated from satellite images. Three types of variables were calculated from the satellite data: spectral variables calculated from a multispectral image, textural variables calculated from a panchromatic image (Tpan) with a 15 × 15 window size, and textural variables calculated from spectral variables (TB+VIs) with a 9 × 9 window size. We compared different mtry and ntree values to find the most suitable parameters for the RF models. The results indicated that the RF model of spectral variables explained 57% (root mean square error (RMSE) = 0.06) of the variability in the field CC data. The soil-adjusted vegetation index (SAVI) and enhanced vegetation index (EVI) were more important than other spectral variables. The RF model of Tpan obtained higher accuracy (R2 = 0.69, RMSE = 0.05) than the spectral variables, and the grey level co-occurrence matrix-based texture measure—Correlation (COR) was the most important variable for Tpan. The most accurate model was obtained from the TB+VIs (R2 = 0.79, RMSE = 0.05), which combined spectral and textural information, thus providing a significant improvement in estimating CC. This model provided an effective approach for detecting the CC of black locust plantations on the Loess Plateau. Numéro de notice : A2018-477 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.3390/f9100623 Date de publication en ligne : 10/10/2018 En ligne : https://doi.org/10.3390/f9100623 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91178 [article]

Simple DEM-based methods to delineate Channel networks for hydrogeomorphological mapping / K. Matsunaga in Transactions in GIS, vol 13 n° 1 (February 2009)  

Public [article]  inTransactions in GIS > vol 13 n° 1 (February 2009) . - pp 87 - 103 Titre : Simple DEM-based methods to delineate Channel networks for hydrogeomorphological mapping Type de document : Article/Communication Auteurs : K. Matsunaga, Auteur ; T. Nakaya, Auteur ; T. Sugai, Auteur Année de publication : 2009 Article en page(s) : pp 87 - 103 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie thématique [Termes IGN] carte géomorphologique [Termes IGN] Chine [Termes IGN] géomorphologie locale [Termes IGN] loess [Termes IGN] MNS SRTM [Termes IGN] modèle numérique de surface [Termes IGN] pente [Termes IGN] plateau [Termes IGN] pondération [Termes IGN] réseau hydrographique Résumé : (Auteur) To delineate channel networks from DEMs regardless of landform type, this article proposes a new method using slope-weighted flow accumulation. To validate the method, SRTM-3, a global DEM dataset with a resolution of approximately 90 m, was used for analysis of the Loess Plateau, China. Channel networks delineated with and without slope-weighted flow accumulation were derived in both uplands and hilly lands for comparison. In the weighted flow accumulation method, the thresholds for delineating the channels were defined by detecting a turning point in the frequency distribution of the weighted flow accumulation function or by visual similarity with drainage channels extracted from topographic maps. The channel networks delineated with weighting showed closer correlation with a topographic map than the channel networks without weighting, despite the differences in thresholds. Moreover, the channel networks delineated with weighting represented the differences between landform types, while the channel networks without weighting did not. Weighting on the basis of the slope angle shows promise as a general channel delineation method which reflects the actual topography due to its hydrogeomorphological functions. Numéro de notice : A2009-546 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1467-9671.2009.01145.x En ligne : https://doi.org/10.1111/j.1467-9671.2009.01145.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30175 [article]

A hemispherical-directional reflectance model as a tool for understanding image distinctions between cultivated and uncultivated bare surfaces / J. Cierniewski in Remote sensing of environment, vol 90 n° 4 (30/04/2004)  

Public [article]  inRemote sensing of environment > vol 90 n° 4 (30/04/2004) . - pp 505 - 523 Titre : A hemispherical-directional reflectance model as a tool for understanding image distinctions between cultivated and uncultivated bare surfaces Type de document : Article/Communication Auteurs : J. Cierniewski, Auteur ; T. Gdala, Auteur ; et al., Auteur Année de publication : 2004 Article en page(s) : pp 505 - 523 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] éclairement lumineux [Termes IGN] Israël [Termes IGN] loess [Termes IGN] photo-identification [Termes IGN] réflectance de surface [Termes IGN] réflectance directionnelle [Termes IGN] réflectance du sol [Termes IGN] rocher [Termes IGN] sol nu [Termes IGN] surface cultivée Résumé : (Auteur) This paper discusses a model to predict the normalized hemispherical -directional reflectance function for soil or rocky surfaces of a given roughness under conditions of outdoor illumination. These surfaces are simulated by geometrical shapes similar to beads merging into each other, characterized by three parameters. In addition, the shape of the surface is characterized by the directivity factor DR, expressing the differences between the maximum and the minimum deviations of its height, calculated along all possible directions. The surface is illuminated by a hemispherical light source created by a number of point sources of given light intensities. The light energy is scattered from the surface, in accordance the quasi-Lambertian function. The distribution of the surface reflectance, as viewed from all the possible directions, can be described for all the possible illumination conditions expressed by the solar zenith and the horizontal angles for a given hemisphere light distribution of a definite optical thickness. This represents the hemispherical -directional reflectance distribution function, HDRDF, of the surface. The HDRDF function is normalized to the nadir viewpoint and visualized for a given illumination condition. The model assumes that the HDRDF of a surface contains information about the directivity of the surface shape, as described by the directivity factor of the surface hemispherical -directional reflectance function DHDRDF. This factor, expressing the asymmetry of the HDRDF with respect to the solar principal plane (SPP), is strongly correlated with the DR. The use of both factors, the DR and DHDRDF, enables us to understand the distinctions between soil surface images with height irregularities of directional character that create a furrow microrelief, and irregularities spread non-directly, randomly, depending on whether the soil has been cultivated or not. The model was tested on directional reflectance data measured in the visible, the near and the middle infrared spectra for cultivated surface with furrows, as well as for three uncultivated desert loess and rocky surfaces situated in Israel. Numéro de notice : A2004-192 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2004.01.004 En ligne : https://doi.org/10.1016/j.rse.2004.01.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26719 [article]

vol 13 n° 2 - 01/03/1988 - Loess: Earth surface processes and landforms (Bulletin de Earth surface processes and landforms) / K.S. Richards

Public [n° ou bulletin]  est un bulletin de Earth surface processes and landforms / British Society for Geomorphology (Royaume-Uni) (1976 -)   Titre : vol 13 n° 2 - 01/03/1988 - Loess: Earth surface processes and landforms Type de document : Périodique Auteurs : K.S. Richards, Éditeur scientifique Année de publication : 1988 Importance : 192 p. Format : 20 x 26 cm Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomorphologie [Termes IGN] Alaska (Etats-Unis) [Termes IGN] Chine [Termes IGN] dune [Termes IGN] loess [Termes IGN] Mississippi (fleuve) [Termes IGN] Tunisie Numéro de notice : 57572 Affiliation des auteurs : non IGN Nature : Numéro de périodique Permalink : https://documentation.ensg.eu/index.php?lvl=bulletin_display&id=6732 [n° ou bulletin]

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Code-barres	Cote	Support	Localisation	Section	Disponibilité
57572-01	47.20	Revue	Centre de documentation	Géographie - Géosciences	Disponible