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A uniform sky illumination model to enhance shading of terrain and urban areas / Patrick Kennelly in Cartography and Geographic Information Science, vol 33 n° 1 (January 2006)
[article]
Titre : A uniform sky illumination model to enhance shading of terrain and urban areas Type de document : Article/Communication Auteurs : Patrick Kennelly, Auteur ; J. Stewart, Auteur Année de publication : 2006 Article en page(s) : pp 21 - 36 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie numérique
[Termes IGN] correction des ombres
[Termes IGN] éclairement lumineux
[Termes IGN] estompage automatique
[Termes IGN] Nevada (Etats-Unis)
[Termes IGN] ombre
[Termes IGN] représentation des détails topographiques
[Termes IGN] système d'information géographique
[Termes IGN] Texas (Etats-Unis)
[Termes IGN] zone urbaineRésumé : (Auteur) Users of geographic information systems (GIS) usually render terrain using a point light source defined by an illumination vector. A terrain shaded from a single point provides good perceptual cues to surface orientation. This type of hill shading, however, does not include any visual cues to the relative height of surface elements. We propose shading the terrain under uniform diffuse illumination, where light arrives equally from all directions of a theoretical sky surrounding the terrain. Surface elements at lower elevations tend to have more of the sky obscured from view and are thus shaded darker. This tinting approach has the advantage that it provides more detailed renderings than point source illumination. We describe two techniques of computing terrain shading under uniform diffuse illumination. One technique uses a GIS-based hill-shading and shadowing tool to combine many point source renderings into one approximating the terrain under uniform diffuse illumination. The second technique uses a C++ computer algorithm for computing the inclination to the horizon in all azimuth directions at all points of the terrain. These virtual horizons are used to map sky brightness to the rendering of the terrain. To evaluate our techniques, we use two Digital Elevation Models (DEMs)-of the Schell Creek Range of eastern Nevada and a portion of downtown Houston, Texas, developed from Light Detection and Ranging (lidar) data. Renderings based on the uniform diffuse illumination model show more detailed changes in shading than renderings based on a point source illumination model. Copyright CaGISociety Numéro de notice : A2006-203 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1559/152304006777323118 En ligne : https://doi.org/10.1559/152304006777323118 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27930
in Cartography and Geographic Information Science > vol 33 n° 1 (January 2006) . - pp 21 - 36[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 032-06011 RAB Revue Centre de documentation En réserve L003 Disponible Application of multiple endmember spectral mixture analysis (MESMA) to AVIRIS imagery for coastal salt marsh mapping: a case study in China Camp, CA, USA / L. Li in International Journal of Remote Sensing IJRS, vol 26 n° 23 (December 2005)
[article]
Titre : Application of multiple endmember spectral mixture analysis (MESMA) to AVIRIS imagery for coastal salt marsh mapping: a case study in China Camp, CA, USA Type de document : Article/Communication Auteurs : L. Li, Auteur ; S.L. Ustin, Auteur ; M. Lay, Auteur Année de publication : 2005 Article en page(s) : pp 5193 - 5207 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] analyse de mélange spectral d’extrémités multiples
[Termes IGN] analyse discriminante
[Termes IGN] analyse multibande
[Termes IGN] bande infrarouge
[Termes IGN] Californie (Etats-Unis)
[Termes IGN] carte de la végétation
[Termes IGN] image AVIRIS
[Termes IGN] littoral
[Termes IGN] marais salé
[Termes IGN] plante halophileRésumé : (Auteur) Multiple endmember spectral mixture analysis (MESMA) was applied to the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) imagery of a salt marsh in China Camp at San Pablo Bay, California, A nine-endmember set representing materials within the scene was used including: two Salicornia and two soils, and Grindelia, Spartina, dry grass, water and shade. The resultant abundance maps were used to investigate the spatial distribution of the marsh vegetation species, Salicornia virginica, Grindelia Stricta and Spartinafoliosa. The Spartina abundance map exhibited a well-defined zone bordering the water and the lower marsh, which is in good agreement with the field observations made in 2002. Comparison of the Salicornia map with all six field global positional system (GPS) polygons indicates Salicornia was classified with high accuracy. The proposed approach did a good job in classifying Spartina and Salicornia which cover 93.81% of the total marsh. The Grindelia fraction image underestimates in some areas, while in other areas it shows false detection. This misclassification is attributed to the spectral similarity between Grindelia and Salicornia and to the small patch size of Grindelia. Further work is required to solve this confusion. Numéro de notice : A2005-514 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/01431160500218911 En ligne : https://doi.org/10.1080/01431160500218911 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27650
in International Journal of Remote Sensing IJRS > vol 26 n° 23 (December 2005) . - pp 5193 - 5207[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 080-05231 RAB Revue Centre de documentation En réserve L003 Exclu du prêt Integrating LIDAR elevation data, multi-spectral imagery and neural network modelling for marsh characterization / J.T. Morris in International Journal of Remote Sensing IJRS, vol 26 n° 23 (December 2005)
[article]
Titre : Integrating LIDAR elevation data, multi-spectral imagery and neural network modelling for marsh characterization Type de document : Article/Communication Auteurs : J.T. Morris, Auteur ; D. Porter, Auteur ; et al., Auteur Année de publication : 2005 Article en page(s) : pp 5221 - 5234 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] Caroline du Sud (Etats-Unis)
[Termes IGN] classification dirigée
[Termes IGN] classification par réseau neuronal
[Termes IGN] données altimétriques
[Termes IGN] données lidar
[Termes IGN] image ADAR
[Termes IGN] image multibande
[Termes IGN] marais salant
[Termes IGN] niveau moyen des mers
[Termes IGN] North American Vertical Datum 1988
[Termes IGN] plante halophile
[Termes IGN] réseau neuronal artificiel
[Termes IGN] sédimentation
[Termes IGN] système de référence géodésiqueRésumé : (Auteur) Vertical elevation relative to mean sea level is a critical variable for the productivity and stability of salt marshes. This research classified a high spatial resolution Airborne Data Acquisition and Registration (ADAR) digital camera image of a salt marsh landscape at North Inlet, South Carolina, USA using an artificial neural network. The remote sensing-derived thematic map was cross-referenced with Light Detection and Ranging (LIDAR) elevation data to compute the frequency distribution of marsh elevation relative to tidal elevations. At North Inlet, the median elevation of the salt marsh dominated by Spartina alterniflora was 0.349m relative to the North American Vertical Datum 1988 (NAVD88), while the mean high water level was 0.618m (2001 to May, 2003) with a mean tidal range of 1.39m. The distribution of elevations of Spartina habitat within its vertical range was normal, and 80% of the salt marsh was situated between a narrow range of 0.22 m and 0.481 m. Areas classified as Juncus marsh, dominated by Juneus roemerianus, had a broader, skewed distribution, with 80% of the distribution between 0.296 m and 0.981 m and a median elevation of 0.519 m. The Juneus marsh occurs within the intertidal region of brackish marshes and along the upper fringe of salt marshes. The relative elevation of the Spartina marsh at North Inlet is consistent with recent work that predicts a decrease in equilibrium elevation with an increasing rate of sea-level rise and suggests that the marshes here have not kept up with an increase in the rate of sea-level rise during the last two decades. Numéro de notice : A2005-515 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/01431160500219018 En ligne : https://doi.org/10.1080/01431160500219018 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27651
in International Journal of Remote Sensing IJRS > vol 26 n° 23 (December 2005) . - pp 5221 - 5234[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 080-05231 RAB Revue Centre de documentation En réserve L003 Exclu du prêt Mapping submergent aquatic vegetation in the US Great Lakes using Quickbird satellite data / P.T. Wolter in International Journal of Remote Sensing IJRS, vol 26 n° 23 (December 2005)
[article]
Titre : Mapping submergent aquatic vegetation in the US Great Lakes using Quickbird satellite data Type de document : Article/Communication Auteurs : P.T. Wolter, Auteur ; C.A. Johnston, Auteur ; G.J. Niemi, Auteur Année de publication : 2005 Article en page(s) : pp 5255 - 5274 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] carte de la végétation
[Termes IGN] données bathymétriques
[Termes IGN] écosystème
[Termes IGN] Etats-Unis
[Termes IGN] Grands Lacs
[Termes IGN] image multitemporelle
[Termes IGN] image Quickbird
[Termes IGN] macrophyte
[Termes IGN] photo-interprétationRésumé : (Auteur) Submergent aquatic vegetation (SAV) is a powerful indicator of environmental conditions in both marine and fresh water ecosystems. Quickbird imagery was used to map SAV at three sites across the Great Lakes. Unsupervised classifications were performed at each site using summer Quickbird sensor data. At one site, a multi-temporal classification approach was added, combining visible red difference (May August) with August red and green visible band data. Multi-temporal SAV classification was superior to single-date results at this site. Muck bottom was not seriously confused with SAV, which was unexpected. Multi-temporal classification results showed less confusion between deep water and SAV, although spectral variability due to sub-surface sandbar structure was a source of error in both single-and multi-date classifications. Nevertheless, some of the confounding effects of water column on SAV classification appear to have been mitigated using this multi-temporal approach. Future efforts would be well served by incorporating detailed, continuous, bathymetry data in the classification process. Quickbird sensor data are very useful for classifying SAV under US Great Lakes conditions. However, regional classification efforts using these data may be impractical at this time, as high cost, rigid tasking parameters and impredictable water conditions limit availability of suitable imagery. Numéro de notice : A2005-516 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/01431160500219208 En ligne : https://doi.org/10.1080/01431160500219208 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27652
in International Journal of Remote Sensing IJRS > vol 26 n° 23 (December 2005) . - pp 5255 - 5274[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 080-05231 RAB Revue Centre de documentation En réserve L003 Exclu du prêt Analysis of long-range network RTK during a severe ionospheric storm / Pawel Wielgosz in Journal of geodesy, vol 79 n° 9 (December 2005)
[article]
Titre : Analysis of long-range network RTK during a severe ionospheric storm Type de document : Article/Communication Auteurs : Pawel Wielgosz, Auteur ; I. Kashani, Auteur ; Dorota A. Grejner-Brzezinska, Auteur Année de publication : 2005 Article en page(s) : pp 524 - 531 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] correction ionosphérique
[Termes IGN] GPS en mode cinématique
[Termes IGN] ionosphère
[Termes IGN] Ohio (Etats-Unis)
[Termes IGN] perturbation ionosphérique
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] résolution d'ambiguïté
[Termes IGN] station GPS
[Termes IGN] station permanente
[Termes IGN] tempête
[Termes IGN] temps réelRésumé : (Auteur) The network-based GPS technique provides a broad spectrum of corrections to support RTK (real-time kinematic) surveying and geodetic applications. The most important among them are the ionospheric corrections generated in the reference network. The accuracy of these corrections depends upon the ionospheric conditions and may not always be sufficient to support ambiguity resolution (AR), and hence accurate GPS positioning. This paper presents the analyses of the network-derived ionospheric correction accuracy under extremely varying quiet and stormy geomagnetic and ionospheric conditions. In addition, the influence of the correction accuracy on the instantaneous (single-epoch) and on-the-fly (OTF) AR in long-range RTK GPS positioning is investigated, and the results, based on post-processed GPS data, are provided. The network used here to generate the ionospheric corrections consists of three permanent stations selected from the Ohio Continuously Operating Reference Stations (CORS) network. The average separation between the reference stations was 200 km and the test baseline was 121 km long. The results show that, during the severe ionospheric storm, the correction accuracy deteriorates to the point when the instantaneous AR is no longer possible, and the OTF AR requires much more time to fix the integers. The analyses presented here also outline the importance of the correct selection of the stochastic constraints in the rover solution applied to the network derived ionospheric corrections. Numéro de notice : A2005-519 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-005-0003-y En ligne : https://doi.org/10.1007/s00190-005-0003-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27655
in Journal of geodesy > vol 79 n° 9 (December 2005) . - pp 524 - 531[article]Réservation
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