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Fluvial gravel bar mapping with spectral signal mixture analysis / Liza Stančič in European journal of remote sensing, vol 54 sup 1 (2021)  

Public [article]  inEuropean journal of remote sensing > vol 54 sup 1 (2021) . - pp 31 - 46 Titre : Fluvial gravel bar mapping with spectral signal mixture analysis Type de document : Article/Communication Auteurs : Liza Stančič, Auteur ; Krištof Oštir, Auteur ; Žiga Kokalj, Auteur Année de publication : 2021 Article en page(s) : pp 31 - 46 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] analyse des mélanges spectraux [Termes IGN] bassin hydrographique [Termes IGN] carte thématique [Termes IGN] gravier [Termes IGN] image Landsat [Termes IGN] image Sentinel-MSI [Termes IGN] précision infrapixellaire [Termes IGN] réflectance spectrale [Termes IGN] rivière [Termes IGN] signature spectrale [Termes IGN] Slovénie Résumé : (auteur) The paper presents a method for mapping fluvial gravel bars based on Sentinel-2 and Landsat imagery. The proposed method therefore uses spectral signal mixture analysis (SSMA) because its results allow the development of land cover fraction maps for surface water, gravel, and vegetation. The method is validated on a spatially heterogeneous mountainous area in the upper Soča river basin in north-west Slovenia, Central Europe. Unmixing results in highly accurate fraction maps with MAE of around 0.1. Gravel fractions are mapped the most accurately, indicating that the approach can be used successfully for fluvial gravel bar mapping. Endmember sets selected automatically perform slightly worse (MAE higher by at most 0.05) than sets selected manually based on high resolution reference data. Both Sentinel-2 and Landsat imagery can be used for accurate mapping with differences between the two remote sensing systems within 0.05 MAE. For the study area, the SSMA-based soft classification method is more accurate for land cover mapping than a Spectral Angle Mapping-based hard classification. The method is promising for an effective use in other cases where highly accurate subpixel information is needed, because it is able to detect small-scale changes that could go unnoticed with hard classification mapping. Numéro de notice : A2021-817 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/22797254.2020.1811776 Date de publication en ligne : 30/08/2020 En ligne : https://doi.org/10.1080/22797254.2020.1811776 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98906 [article]

Study on offshore seabed sediment classification based on particle size parameters using XGBoost algorithm / Fengfan Wang in Computers & geosciences, vol 149 (April 2021)  

Public [article]  inComputers & geosciences > vol 149 (April 2021) . - n° 104713 Titre : Study on offshore seabed sediment classification based on particle size parameters using XGBoost algorithm Type de document : Article/Communication Auteurs : Fengfan Wang, Auteur ; Jia Yu, Auteur ; Zhijie Liu, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 104713 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] analyse spatiale [Termes IGN] calcul matriciel [Termes IGN] Chine [Termes IGN] classification par forêts d'arbres décisionnels [Termes IGN] classification par séparateurs à vaste marge [Termes IGN] diagramme [Termes IGN] échantillon [Termes IGN] Extreme Gradient Machine [Termes IGN] fond marin [Termes IGN] gravier [Termes IGN] image à haute résolution [Termes IGN] sédiment Résumé : (auteur) Folk's textual classification scheme which is widely used for sediment study operates with the proportions of gravel, sand, silt and clay fractions conventionally. However, dealing with data from different sources usually needs to face missing values that may make the classification difficult. To solve this problem and discover other methods of analyzing the scheme, with samples of offshore seabed sediment, a two-stage model was established to predict a sample's class using the XGBoost algorithm as well as the grain size parameters as input features. The final model was evaluated with quantitative performance measures of recall, precision and F1 score, and by comparing sediment texture maps using the predicted and the actual data. The results show that the model performs well on extraction of sediment samples without gravel fraction, and prediction of classes that have independent characteristics of grain size parameters or samples not near the boundaries of classes in the ternary diagram. The predicted sediment texture is close to the actual and could be reliable due to errors with little impact on further applications. It is demonstrated that the model could be an auxiliary or alternative approach to offshore sediment texture mapping, as well as supplementary to the analysis of sedimentary environment. Numéro de notice : A2021-289 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1016/j.cageo.2021.104713 Date de publication en ligne : 12/02/2021 En ligne : https://doi.org/10.1016/j.cageo.2021.104713 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97400 [article]

A merging solution for close-range DEMs to optimize surface coverage and measurement resolution / Stéphane Bertin in Photogrammetric Engineering & Remote Sensing, PERS, vol 82 n° 1 (January 2016)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 82 n° 1 (January 2016) . - pp 31 – 40 Titre : A merging solution for close-range DEMs to optimize surface coverage and measurement resolution Type de document : Article/Communication Auteurs : Stéphane Bertin, Auteur ; Heide Friedrich, Auteur ; Patrice Delmas, Auteur Année de publication : 2016 Article en page(s) : pp 31 – 40 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] étalonnage des données [Termes IGN] fusion de données [Termes IGN] gravier [Termes IGN] intégration de données [Termes IGN] lit [Termes IGN] modèle numérique de surface [Termes IGN] photogrammétrie métrologique [Termes IGN] torrent Résumé : (auteur) The process of efficient and effective DEM merging is increasingly becoming more important. To allow DEM analysis for features of different scales, an increase in surface coverage cannot result in reduced measurement resolution. It is thus inevitable that merging individual high-resolution DEMs will become common practice for applications such as hydraulic roughness studies for fluvial surfaces. This paper presents an efficient and effective merging solution, whereby accurate co-registration of individual DEMs collected from consistent viewpoints and standard averaging for overlapping elevations ensure seamless merging. The presented method is suitable for DEMs collected using any measurement technology, as long as individual DEMs overlap and are arranged on regular grids. The merging solution is applied to the study of a laboratory gravel bed measured with vertical stereo photogrammetry at the grain scale (>106 points/ m2). We show that the approach can be integrated into the DEM collection workflow at the design stage, which optimizes the measurement performance. We present how resampling before merging can be beneficial to keep data handling requirements practical, whilst ensuring accurate surface representation. Finally, the effect of scale variation is studied, showing that seamless merging applies to DEMs with variable resolution. Numéro de notice : A2016-049 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.83.1.31 En ligne : https://doi.org/10.14358/PERS.83.1.31 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79653 [article]

DEM measurements of a gravel-bed surface using two scales of images / Chi-Kuei Wang in Photogrammetric record, vol 30 n° 152 (December 2015 - February 2016)  

Public [article]  inPhotogrammetric record > vol 30 n° 152 (December 2015 - February 2016) . - pp 387 - 401 Titre : DEM measurements of a gravel-bed surface using two scales of images Type de document : Article/Communication Auteurs : Chi-Kuei Wang, Auteur ; Jui-Teng Chung, Auteur ; Yu-Li Lin, Auteur Année de publication : 2015 Article en page(s) : pp 387 - 401 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] gravier [Termes IGN] limite de résolution géométrique [Termes IGN] lit [Termes IGN] modèle numérique de surface [Termes IGN] photogrammétrie terrestre [Termes IGN] rivière [Termes IGN] Taïwan Résumé : (auteur) Determining the geometry of an exposed gravel-bed surface is important in understanding river flow characteristics. This study presents a method of generating a digital elevation model (DEM) of exposed gravel-bed surfaces using two different scales of images of a riverine environment. The small scale DEM covers an area of 4·5 m × 4·5 m and serves as the reference base, whereas several large scale DEMs provide highly detailed elevation information along the site diagonals. The equipment includes a consumer-grade camera and is light and easy to set up in the field. Highly automated procedures using several off-the-shelf packages ease the burden of generating DEMs of the gravel-bed surface, reducing the technological obstacles for other disciplines. This study evaluates the accuracy of the proposed method at three study sites with different grain sizes along the Hou-Jue River in southern Taiwan. The elevation accuracy obtained by the proposed method was validated by a total station and achieved a root mean square error of 2·9 to 4·3 mm. Numéro de notice : A2015-828 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1111/phor.12125 Date de publication en ligne : 15/12/2015 En ligne : https://doi.org/10.1111/phor.12125 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79124 [article]

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106-2015041	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Bidirectional reflectance spectrometry of gravel at the Sjökulla test field / J. Peltoniemi in ISPRS Journal of photogrammetry and remote sensing, vol 62 n° 6 (November-December 2007)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 62 n° 6 (November-December 2007) . - pp 434 - 446 Titre : Bidirectional reflectance spectrometry of gravel at the Sjökulla test field Type de document : Article/Communication Auteurs : J. Peltoniemi, Auteur ; J. Piironen, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 434 - 446 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] analyse diachronique [Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF [Termes IGN] étalonnage radiométrique [Termes IGN] étalonnage spectral [Termes IGN] gravier [Termes IGN] image aérienne [Termes IGN] test de performance Résumé : (Auteur) The Sjökulla test site is used for testing and calibrating aerial images. The permanent test field is made of four types of gravel (dark gabbro, grey granite, red granite, white limestone) in two sizes (diameters 8–16 mm and 4–8 mm) set in various patterns. The bidirectional reflection properties of the targets together with their temporal changes must be known in order to carry out radiometric and spectral evaluation and calibration. The bidirectional reflectance distribution functions (BRF) of the gravel have been measured several times in the test fields using portable field goniospectrometers belonging Finnish Geodetic Institute (FGI), and once using the European Goniometic Facility (EGO) of the Joint Research Centre (JRC) at Ispra, Italy. Detailed BRFs have been obtained, showing features typical to particulate media, e.g. a small bowl shape, strong backscattering, and smooth wavelength dependence. Temporal range measurements over several years show that the black gabbro and red granite are fairly stable, while the grey granite has changed somewhat over the years and the white limestone has experienced dramatic darkening effects, requiring action to be taken. The measured BRF data have increased the usability of the test field considerably. The results are also useful in the development and validation of scattering models for particulate media. The site has proved to be a good test bench for goniospectrometric instruments, too. Copyright ISPRS Numéro de notice : A2007-529 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2007.07.009 En ligne : https://doi.org/10.1016/j.isprsjprs.2007.07.009 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28892 [article]

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