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Impact of scale and quality of Digital Terrain Models on predictability of seabed terrain types / Lars Erikstad in Marine geodesy, vol 36 n° 1 (January - March 2013)  

Public [article]  inMarine geodesy > vol 36 n° 1 (January - March 2013) . - pp 2 - 21 Titre : Impact of scale and quality of Digital Terrain Models on predictability of seabed terrain types Type de document : Article/Communication Auteurs : Lars Erikstad, Auteur ; Vegar Bakkestuen, Auteur ; Trine Bekkby, Auteur ; Rune Halvorsen, Auteur Année de publication : 2013 Article en page(s) : pp 2 - 21 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] fond marin [Termes IGN] habitat animal [Termes IGN] modèle numérique bathymétrique [Termes IGN] Norvège [Termes IGN] pente [Termes IGN] relief sous-marin Résumé : (Auteur) The local and regional distribution of seabed terrain types depends on factors such as slope and terrain ruggedness. Digital bathymetrical models (DBM) are therefore essential for mapping and predictive modeling of marine habitats. DBMs vary considerably with respect to scale and quality, and this variation is likely to influence the predictive ability of marine habitat models built with use of DBM-derived environmental predictor variables. We studied the interpretability of seabed terrain types from four different DBMs in two ways: by visual inspection of hillshade representation of the DBMs and by subjecting sets of variables derived from each of the four DBMs to maximum entropy (MaxEnt) predictive modeling of six seabed terrain types. Our results show that DBMs based on multibeam echo sounder data, resampled at resolutions up to 50 m, enable identification of concentrations of seabed terrain types characterized by moraine-ridge assemblies and plough-mark fields. Variables derived from models interpolated from contours of existing marine maps and bathymetric databases have strong limitations and merely enable separation of terrain dominated by rugged bedrock seabed from soft sediment flats. Interpolated DBMs are currently the only type of bathymetrical data that cover all Norwegian coastal waters. Their poor quality is an important obstacle to predictive modeling and classification of seabed habitats. Numéro de notice : A2013-243 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/01490419.2012.747454 Date de publication en ligne : 13/03/2013 En ligne : https://doi.org/10.1080/01490419.2012.747454 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32381 [article]

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Study on the new methods of ship object detection based on GNSS reflection / Yong Lu in Marine geodesy, vol 36 n° 1 (January - March 2013)  

Public [article]  inMarine geodesy > vol 36 n° 1 (January - March 2013) . - pp 22 - 30 Titre : Study on the new methods of ship object detection based on GNSS reflection Type de document : Article/Communication Auteurs : Yong Lu, Auteur ; Dongkai Yang, Auteur ; Weiqiang Li, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 22 - 30 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] capteur aérien [Termes IGN] détection d'objet [Termes IGN] navire [Termes IGN] réflectométrie par GNSS Résumé : (Auteur) This paper presents a study on the new methods of ship object detection based on GPS-R correlation power spectra. Both the principle and the algorithms for recognition are given in detail. The architecture of Doppler Delay Mapping Receiver (DDMR), signal-processing chain, and correlation power spectra discriminant of the reflected signals from the ship object are discussed. Real-time data collection campaigns were done near the sea at Sanya with the Doppler delay mapping receiver mounted on an airplane. Some preliminary experiment results show that the DDMR could work well and can be used in ship object detecting. Numéro de notice : A2013-244 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2012.747456 Date de publication en ligne : 13/03/2013 En ligne : https://doi.org/10.1080/01490419.2012.747456 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32382 [article]

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Lowest astronomical tide in the North Sea derived from a vertically referenced shallow water model, and an assessment of its suggested sense of safety / D. Slobbe in Marine geodesy, vol 36 n° 1 (January - March 2013)  

Public [article]  inMarine geodesy > vol 36 n° 1 (January - March 2013) . - pp 31 - 71 Titre : Lowest astronomical tide in the North Sea derived from a vertically referenced shallow water model, and an assessment of its suggested sense of safety Type de document : Article/Communication Auteurs : D. Slobbe, Auteur ; R. Klees, Auteur ; M. Verlaan, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 31 - 71 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Océanographie [Termes IGN] géoïde local [Termes IGN] geoïde marin [Termes IGN] marée océanique [Termes IGN] niveau de la mer [Termes IGN] niveau moyen des mers [Termes IGN] Nord, mer du [Termes IGN] réduction Résumé : (Auteur) Water level reduction with global navigation satellite systems in bathymetric surveying requires knowledge of the ellipsoidal heights of lowest astronomical tide (LAT). The traditional approach uses tidal water levels of an ocean tide model, which are subtracted from mean sea level (MSL). This approach has two major drawbacks: the modeled water levels refer to an equipotential surface, which differs from MSL, and MSL may not be known close to the coast. Here, we propose to model LAT directly relative to an equipotential surface (geoid). This is conceptually consistent with the flow equations and allows the inclusion of temporal MSL variations into the LAT definition. Numerical experiments for the North Sea show that significant differences between the traditional and the pursued approach exist if average monthly variations in MSL are included. A validation of the modeled LAT using tide gauge records reveals systematic errors, which we attribute to both the model and the tidal analysis procedure. We also show that the probability that water levels drop below LAT is high, with maximum frequency of once per week in the eastern North Sea. Therefore, we propose to reconsider the deterministic concept of LAT by a probabilistic chart datum concept, and we quantified the differences between them. Numéro de notice : A2013-245 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2012.743493 Date de publication en ligne : 13/03/2013 En ligne : https://doi.org/10.1080/01490419.2012.743493 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32383 [article]

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Comparison of grid averaged altimeter and buoy significant wave heights in the Northern Indian Ocean / L. Sabique in Marine geodesy, vol 36 n° 1 (January - March 2013)  

Public [article]  inMarine geodesy > vol 36 n° 1 (January - March 2013) . - pp 72 - 85 Titre : Comparison of grid averaged altimeter and buoy significant wave heights in the Northern Indian Ocean Type de document : Article/Communication Auteurs : L. Sabique, Auteur ; T. Balakrishnan Nair, Auteur ; K. Srinivas, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 72 - 85 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] altimétrie satellitaire par radar [Termes IGN] analyse diachronique [Termes IGN] AVISO [Termes IGN] bouée [Termes IGN] bouée dérivante [Termes IGN] cyclone [Termes IGN] hauteurs de mer [Termes IGN] Indien (océan) [Termes IGN] série temporelle [Termes IGN] vague Résumé : (Auteur) A quantitative comparison of the collocated inter-annual significant wave height (SWH) data collected between 2006 and 2009 from buoys and altimeters at nine buoy locations (total n = 2241) in the Northern Indian Ocean is attempted for assessing the validity of daily averaged gridded altimeter significant wave height (ASWH) provided by AVISO for operational use. ASWH is underestimated by 0.20 m, the root-mean-square error (RMSE) is less than 0.30 m, the Scatter Index is less than 20%, and the correlation coefficient is greater than 0.90. Further, at three locations, the examination of the above statistics showed that the bias and RMSE is high during the southwest monsoon season compared with the Northeast monsoon. Scatter Index showed only slight variation (14–18%) for different ranges of SWH. The response of the daily average gridded ASWH data during extreme conditions (cyclones) in the vicinity of the buoy locations is poor at all compared buoy locations. The gridded ASWH from different satellite missions provided by AVISO can be used for basin scale validation experiments of the wave model and for climatological studies in the Indian Ocean, except during cyclone conditions. Numéro de notice : A2013-246 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2012.743493 Date de publication en ligne : 13/03/2013 En ligne : https://doi.org/10.1080/01490419.2012.743493 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32384 [article]

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Tsunami inundation modelling for the coast of Kerala, India / S. Praveen in Marine geodesy, vol 36 n° 1 (January - March 2013)  

Public [article]  inMarine geodesy > vol 36 n° 1 (January - March 2013) . - pp 86 - 97 Titre : Tsunami inundation modelling for the coast of Kerala, India Type de document : Article/Communication Auteurs : S. Praveen, Auteur ; N. Kurian, Auteur ; T. Hameed, Auteur Année de publication : 2013 Article en page(s) : pp 86 - 97 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bathymétrie [Termes IGN] inondation [Termes IGN] Kerala (Inde ; état) [Termes IGN] modèle numérique bathymétrique [Termes IGN] montée du niveau de la mer [Termes IGN] niveau de la mer [Termes IGN] tsunami Résumé : (Auteur) The disastrous tsunami of December 26, 2004, exposed the urgent need for implementing a tsunami warning system. One of the essential requirements of a tsunami warning system is the set up of tsunami inundation models which can predict inundation and run-up along a coastline for a given set of seismic parameters. The Tsunami Warning Centre and the State/District level Disaster Management Centres should have tsunami inundations maps for different scenarios of tsunami generation. In the event of a tsunamigenic earthquake, appropriate decisions on issue of warnings and/or evacuation of coastal population are made by referring to such maps. The nature of tsunami inundation and run-up along the Kerala coast for the 2004 Sumatra and 1945 Makran, and a hypothetical worst-case scenario are simulated using the TUNAMI N2 model and the results are presented in this paper. Further, scenarios of tsunami inundation arising out of possible rise in sea level as projected by the Intergovernmental Panel on Climate Change (IPCC 2001) are also simulated and analysed in the paper. For the study, three representative sectors of the Kerala coast including the Neendakara-Kayamkulam coast, which was the worst hit by the 2004 tsunami, are chosen. The results show that the southern locations and certain locations of central Kerala coast are more vulnerable for Sumatra when compared to Makran 1945 tsunami. From the results of numerical modelling for future scenarios it can be concluded that sea level rise can definitely make pronounced increase in inundation in some of the stretches where the backshore elevation is comparatively low. Numéro de notice : A2013-247 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2012.699502 Date de publication en ligne : 13/03/2013 En ligne : https://doi.org/10.1080/01490419.2012.699502 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32385 [article]

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Performance of real-time precise point positioning / Junping Chen in Marine geodesy, vol 36 n° 1 (January - March 2013)  

Public [article]  inMarine geodesy > vol 36 n° 1 (January - March 2013) . - pp 98 - 108 Titre : Performance of real-time precise point positioning Type de document : Article/Communication Auteurs : Junping Chen, Auteur ; Haojun Li, Auteur ; Bin Wu, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 98 - 108 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] horloge atomique [Termes IGN] orbite [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur monofréquence [Termes IGN] temps réel Résumé : (Auteur) The IGS Real-time Pilot Project (IGS-RTPP) provides real-time precise orbits and clocks, which support real-time positioning for single stations over large areas using the Precise Point Positioning (PPP) technique. This paper investigates the impact of real-time orbits, network configuration, and analysis strategies on real-time PPP implementation and demonstrates the real-time PPP performance. One month of data from the IGS network is analyzed in a real-time simulation mode. Results reveal the following: (1) In clock estimation, differential approaches are much more efficient than the zero-differenced approach. (2) The precision of IGS Ultra rapid (IGU) orbits could meet the IGS-RTPP requirement for precise clock estimation and PPP positioning. (3) Considering efficiency and precision, a network with 50 stations is recommended for the IGS-RTPP. It is demonstrated that the real-time satellite clock precision is 0.1 ns supporting hourly static PPP with a mean precision of 2–3 cm in the North component and 3–4 cm in the other components. Kinematic PPP assessed with onboard GPS data collected from a buoy provided mean coordinate precision of 2.2, 4.2, 6.1 cm in the North, East and Up directions, compared to the RTK solutions. Numéro de notice : A2013-248 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2012.699503 Date de publication en ligne : 13/03/2013 En ligne : https://doi.org/10.1080/01490419.2012.699503 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32386 [article]

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