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Can ensemble techniques improve coral reef habitat classification accuracy using multispectral data? / Mohammad Shawkat Hossain in Geocarto international, vol 35 n° 11 ([01/08/2020])  

Public [article]  inGeocarto international > vol 35 n° 11 [01/08/2020] . - pp 214 - 1232 Titre : Can ensemble techniques improve coral reef habitat classification accuracy using multispectral data? Type de document : Article/Communication Auteurs : Mohammad Shawkat Hossain, Auteur ; Aidy M. Muslim, Auteur ; Muhammad Izuan Nadzri, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 214 - 1232 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes descripteurs IGN] biodiversité [Termes descripteurs IGN] carte bathymétrique [Termes descripteurs IGN] Chine, mer de [Termes descripteurs IGN] classification barycentrique [Termes descripteurs IGN] classification hypercube [Termes descripteurs IGN] classification par maximum de vraisemblance [Termes descripteurs IGN] distribution de Fisher [Termes descripteurs IGN] fond marin [Termes descripteurs IGN] image multibande [Termes descripteurs IGN] Malaisie [Termes descripteurs IGN] précision de la classification [Termes descripteurs IGN] récif corallien [Termes descripteurs IGN] réflectance spectrale Résumé : (auteur) Remote sensing has potential in studies of the benthic habitat and extracting the reflectance from the data of multispectral sensors, but traditional image classification techniques cannot provide coral habitat maps with adequate accuracy. This study tested five traditional and three ensemble classification techniques on QuickBird for mapping the benthic composition of coral reefs on the Lang Tengah Island (Malaysia). The common techniques, minimum distance, maximum likelihood, K-nearest neighbour, Fisher and parallelepiped techniques were compared with ensemble classifiers, such as majority voting (MV), simple averaging, and mode combination. The per-class accuracy of the habitat detection improved in the ensemble classifiers; in particular, the MV classifier achieved 95%, 65%, 75% and 95% accuracies for coral, sparse coral, coral rubble and sand, respectively. Ensembles increased the accuracy of the habitat mapping classification by 28%, relative to conventional techniques. Thus, the ensemble techniques can be preferred over the traditional for benthic habitat mapping. Numéro de notice : A2020-459 Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10106049.2018.1557263 date de publication en ligne : 12/02/2019 En ligne : https://doi.org/10.1080/10106049.2018.1557263 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95566 [article]

Long time-series remote sensing analysis of the periodic cycle evolution of the inlets and ebb-tidal delta of Xincun Lagoon, Hainan Island, China / Huaguo Zhang in ISPRS Journal of photogrammetry and remote sensing, vol 165 (July 2020)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 165 (July 2020) . - pp 67 - 85 Titre : Long time-series remote sensing analysis of the periodic cycle evolution of the inlets and ebb-tidal delta of Xincun Lagoon, Hainan Island, China Type de document : Article/Communication Auteurs : Huaguo Zhang, Auteur ; Dongling Li, Auteur ; Juan Wang, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 67 - 85 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes descripteurs IGN] cyclone [Termes descripteurs IGN] delta [Termes descripteurs IGN] fond marin [Termes descripteurs IGN] Hainan (Chine) [Termes descripteurs IGN] lagune [Termes descripteurs IGN] marée océanique [Termes descripteurs IGN] marégraphie [Termes descripteurs IGN] message d'alerte [Termes descripteurs IGN] modèle conceptuel de données spatio-temporelles [Termes descripteurs IGN] précipitation [Termes descripteurs IGN] sable [Termes descripteurs IGN] série temporelle [Termes descripteurs IGN] surveillance du littoral [Termes descripteurs IGN] variation temporelle Résumé : (auteur) Coastal lagoon–tidal inlet systems occur worldwide, and each has its own unique evolution characteristics in relation to its geographical location, sediment characteristics, and tidal current and ocean wave conditions. However, insufficient observation data means that it is often difficult to fully understand the long-term and short-term evolution of ebb-tidal deltas, and it is even more difficult to monitor and warn against their evolution. This study uses long time-series remote sensing data for the period 1962–2018 to investigate the evolution of an ebb-tidal delta in Xincun Lagoon, Hainan Island, China. Four shoal-sandbar breaching and tidal-inlet migration events were observed, and the corresponding periodic variation characteristics of the ebb-tidal delta were documented. A conceptual model for the periodic evolution of ebb-tidal deltas was also proposed. The results showed that the long-period (15–20 years) evolution was controlled by the effects of seabed friction and tidal-scale lagoon resonance, while the changes in the length of the east sand-spit could be used as a significant early warning indicator for shoal-sandbar breaching and tidal-inlet migration events. In addition, both types of event were jointly triggered by typhoon storm-surges and the accompanying heavy rainfall, strong winds, and strong waves. Thus, the periodic evolution process of the ebb-tidal delta in Xincun Lagoon was determined to be a systematic process that is either controlled or influenced by a series of interconnecting factors. Moreover, we concluded that it is both feasible and valuable to establish a monitoring and early warning framework of ebb-tidal deltas through the use of time-series remote sensing images. The results of this study can improve the existing understanding of the processes and driving factors of periodic shoal-sandbar breaching and tidal-inlet migration, and can also increase safety nourishment for coastal lagoon–tidal inlet systems. Numéro de notice : A2020-348 Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2020.05.006 date de publication en ligne : 26/05/2020 En ligne : https://doi.org/10.1016/j.isprsjprs.2020.05.006 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95230 [article]

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Improving GNSS-acoustic positioning by optimizing the ship’s track lines and observation combinations / Guanxu Chen in Journal of geodesy, vol 94 n° 6 (June 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 6 (June 2020) Titre : Improving GNSS-acoustic positioning by optimizing the ship’s track lines and observation combinations Type de document : Article/Communication Auteurs : Guanxu Chen, Auteur ; Yang Liu, Auteur ; Yanxiong Liu, Auteur ; et al., Auteur Année de publication : 2020 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes descripteurs IGN] contrainte géométrique [Termes descripteurs IGN] fond marin [Termes descripteurs IGN] GNSS-Acoustique [Termes descripteurs IGN] navire [Termes descripteurs IGN] positionnement par GNSS [Termes descripteurs IGN] précision du positionnement [Termes descripteurs IGN] profondeur [Termes descripteurs IGN] station GNSS [Termes descripteurs IGN] trajectoire Résumé : (auteur) The position of a seafloor geodetic station can be determined by combining Global Navigation Satellite System (GNSS) and acoustic technologies, called GNSS-acoustic positioning. The precision of GNSS-acoustic positioning, a technique that employs the distance intersection, is determined by the positioning geometry formed by the ship’s track lines with respect to the seafloor station and the errors in the measurements. In the context of a shallow sea trial, we studied three key techniques in GNSS-acoustic positioning: the optimal geometric configuration, differencing techniques for acoustic observations and depth constraints offered by pressure gauges. The results showed that the optimal geometric configuration is a circular track with a radius of 2‾√ times the depth plus an overhead cross-track with a length of the circle diameter. Differenced observations can improve the horizontal positioning precision but will worsen the vertical positioning precision due to the change in the geometric configuration and the elimination of vertical information if the number of observations is limited. The proposed difference strategy, that is, applying a symmetric location difference operator to the circular track and an undifference operator to the cross-track, can effectively improve the horizontal precision and avoid vertical defects. By using relative depth observations from two pressure gauges as constraints, the vertical defects of GNSS-acoustic positioning can be improved, achieving a better vertical positioning precision. Applying the proposed methods to high-quality GNSS and acoustic observations, the positioning precision of a shallow seafloor geodetic station can be better than 2 cm. Numéro de notice : A2020-377 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern date de publication en ligne : 27/06/2020 En ligne : https://doi.org/10.1007/s00190-020-01389-1 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95369 [article]

Filtering of airborne LiDAR bathymetry based on bidirectional cloth simulation / Anxiu Yang in ISPRS Journal of photogrammetry and remote sensing, vol 163 (May 2020)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 163 (May 2020) . - pp 49 - 61 Titre : Filtering of airborne LiDAR bathymetry based on bidirectional cloth simulation Type de document : Article/Communication Auteurs : Anxiu Yang, Auteur ; Fanlin Yang, Auteur ; Dianpeng Su, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 49 - 61 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes descripteurs IGN] ajustement de paramètres [Termes descripteurs IGN] Chine [Termes descripteurs IGN] courbe de Gauss [Termes descripteurs IGN] données lidar [Termes descripteurs IGN] filtrage de points [Termes descripteurs IGN] itération [Termes descripteurs IGN] lidar bathymétrique [Termes descripteurs IGN] relief sous-marin [Termes descripteurs IGN] semis de points [Termes descripteurs IGN] télémétrie laser aéroporté Résumé : (auteur) Current filtering methods of airborne LiDAR bathymetry (ALB) point clouds cannot identify negative anomalies or avoid over-filtering of the data. To overcome these problems, we propose a bidirectional cloth simulation filtering (BCSF) method and verify it using captured data. First, a transfer iterative trend surface is established to eliminate the negative anomalies and realize the continuous expression of the seafloor topography. The terrain complexities of the seafloor points are calculated using four extracted feature factors: slope, standard deviation of depth, Gaussian curvature, and roughness. We then calculate the sub-regional terrain complexity and the adaptive distance threshold and obtain user-defined parameters. Finally, sub-regional filtering is carried out, and a filtered surface is established to solve the over-filtering problem of convex and concave seafloor topographies based on the BCSF correction model. To evaluate the performance of the proposed method, the BCSF method was applied to ALB data captured around Yuanzhi Island in the South China Sea. The experimental results show that the BCSF method effectively filters out non-seafloor points and fully preserves the seafloor microtopography to realize the integrity of the seafloor topography. The proposed BCSF method outperforms the cloth simulation filtering method in terms of the elimination rate, which decreases from 38.78% to 2.52% and from 29.52% to 0.70% in the whole study area and local study area, respectively. Consequently, the BCSF method that combines forward filtering with inverse filtering exhibits complementary advantages, avoids over-filtering, and demonstrates strong adaptability and robustness for ALB data. Numéro de notice : A2020-137 Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2020.03.004 date de publication en ligne : 09/03/2020 En ligne : https://doi.org/10.1016/j.isprsjprs.2020.03.004 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94755 [article]

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Applying iterative method to solving high-order terms of seafloor topography / Diao Fan in Marine geodesy, Vol 43 n° 1 (janvier 2020)  

Public [article]  inMarine geodesy > Vol 43 n° 1 (janvier 2020) . - pp 63 - 85 Titre : Applying iterative method to solving high-order terms of seafloor topography Type de document : Article/Communication Auteurs : Diao Fan, Auteur ; Shanshan Li, Auteur ; Shuyu Meng, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 63 - 85 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie [Termes descripteurs IGN] Chine, mer de [Termes descripteurs IGN] fond marin [Termes descripteurs IGN] force de gravitation [Termes descripteurs IGN] gravimétrie en mer [Termes descripteurs IGN] inversion [Termes descripteurs IGN] itération [Termes descripteurs IGN] relief sous-marin Résumé : (auteur) We introduce an iterative inversion method to address the problems in high-order seafloor topography inversion using gravity data (gravity anomaly and vertical gravity gradient anomaly), such as the difficulty in computing the equation and the uniqueness of the calculation results. A part of the South China Sea is selected as the experimental area. Considering the coherence and admittance function of gravity topography and vertical gravity gradient topography, the inversion band of the gravity anomaly and vertical gravity gradient anomaly in the study area is 30 km–120 km. Seafloor topography models of different orders are constructed using an iterative method, and the performance of each seafloor topography model is analyzed against ETOPO1 and other seafloor topography models. The experimental results show that as the inversion order increases, the clarity and richness of seafloor topographic expression continuously improve. However, the accuracy of seafloor topography inversion does not improve significantly when the inversion order exceeds a certain value, which is related to the contribution of high-order seafloor topography to gravity information. The results show that the accuracy of BGT4 (inversion model constructed by the gravity anomaly) is slightly poorer than that of BVGGT4 (inversion model constructed by the vertical gravity gradient anomaly) in areas with complex topography, such as multi-seamounts and trenches, and the results are generally better in areas with flat seafloor topography. Numéro de notice : A2020-463 Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2019.1670298 date de publication en ligne : 08/10/2019 En ligne : https://doi.org/10.1080/01490419.2019.1670298 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95125 [article]

Photogrammetric Bathymetry for the Canadian Arctic / Matus Hodul in Marine geodesy, Vol 43 n° 1 (janvier 2020)  

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Towards new applications of underwater photogrammetry for investigating coral reef morphology and habitat complexity in the Myeik Archipelago, Myanmar / Martina Anelli in Geocarto international, vol 34 n° 5 ([01/05/2019])  

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Mise en place d’un système sondeur multifaisceaux dans une embarcation légère semi-rigide pour campagne de mesure bathymétrique et couplage avec un scanner terrestre, GNSS et INS / Alexandre Girard (2019)

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Estimated location of the seafloor sources of marine natural oil seeps from sea surface outbreaks : A new "source path procedure" applied to the northern Gulf of Mexico / Zhour Najoui in Marine and Petroleum Geology, Vol 91 (March 2018)  

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Analyse du bilan d’erreur appliquée aux systèmes de levés hydrographiques de surface et sous-marin / Geraud Naankeu-Wati in XYZ, n° 152 (septembre - novembre 2017)

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Shipborne over- and under-water integrated mobile mapping system and its seamless integration of point clouds / Bo Shi in Marine geodesy, vol 40 n° 2-3 (March - June 2017)  

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Cartographie, les profondeurs en 3D / Marielle Mayo in Géomètre, n° 2139 (septembre 2016)

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La mission Topex-Poséidon d'altimétrie spatiale / Anonyme in Géomètre, n° 2139 (septembre 2016)

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Feature-driven generalization of isobaths on nautical charts: A multi-agent system approach / Eric Guilbert in Transactions in GIS, vol 20 n° 1 (February 2016)  

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Acquisition et reconstruction de données 3D denses sous-marines en eau peu profonde par des robots d'exploration / Loïca Avanthey (2016)  

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