An iterative Extended Kalman Filter (EKF) approach is proposed to recover a regional set of topog... more An iterative Extended Kalman Filter (EKF) approach is proposed to recover a regional set of topographic heights composing an undersea volcanic mount by the successive combination of large numbers of gravity measurements at sea surface using altimetry satellite-derived grids and taking the error uncertainties into account. The integration of the non-linear Newtonian operators versus the radial and angular distances (and its first derivatives) enables the estimation process to accelerate and requires only few iterations, instead of summing Legendre polynomial series or using noise-degraded 2D-FFT decomposition. To show the effectiveness of the EKF approach, we apply it to the real case of the bathymetry around the Great Meteor seamount in the Atlantic Ocean by combining only geoid height/free-air anomaly datasets and using ship-track soundings as reference for validation. Topography of the Great Meteor seamounts structures are well-reconstructed, especially when regional compensation ...
<p>The AGOSTA project initially proposed by our team and lately funded by CNES TOSCA consis... more <p>The AGOSTA project initially proposed by our team and lately funded by CNES TOSCA consists of developing efficient approaches to restore seafloor shape (or bathymetry), as well as lithospheric parameters such as the crust and elastic thicknesses, by combining different types of observations including gravity gradient data. As it is based on the second derivatives of the potential versus the space coordinates, gravity gradiometry provides more information inside the Earth system at short wavelengths. The GOCE mission has measured the gravity gradient components of the static field globally and give the possibility to detect more details on the structure of the lithosphere at spatial resolutions less than 200 km. We propose to analyze these satellite-measured gravity tensor components to map the undersea relief more precisely than using geoid or vertical gravity previously considered for this purpose. Inversion of vertical gravity gradient data derived from the radar altimetry technique also offers the possibility to reach greater resolutions (at least 50 km) than the GOCE mission one. The seafloor topography estimates are tested in areas well-covered by independent data for validation, such as around the Great Meteor guyot [29&#176;57&#8242;10.6&#8243;N, 28&#176;35&#8242;31.3&#8243;W] and New England seamount chain [37&#176;24&#8242;N 60&#176;00&#8242;W, 120&#176; 10' 30.4" W] in the Atlantic Ocean as well as the Acapulco seamount [13&#176; 36' 15.4" N, 120&#176; 10' 30.4" W] in the Central Pacific.</p>
Morphology and movements of sand dunes are studied using repeated high-resolution bathymetric dat... more Morphology and movements of sand dunes are studied using repeated high-resolution bathymetric data in areas where banner banks approach the shore. Two sites in the Bristol Channel were selected for their contrasting environments. The Helwick Sands is characterised by deeper water-depths, stronger wave climates and weaker tidal currents than the Nash Sands. At the Helwick, migrations of the dunes were measured ranging between 21 and 109 hlv"1. Dunes crossing its crest and connecting despite opposite direction of migration on either flank were observed. This geometry is interpreted to be the result of the strong wave climate coupled with a nearly rectilinear tidal flow, which are leading to dune crests extension. A morphometric study of the sand dunes has revealed the tendency for the dunes to flatten in shallow water, which can also be attributed to the effect of the waves. At the Nash, strong currents and breaking waves have created a strong crestal escarpment. Dune migration r...
&lt;p&gt;Access to marine data is a key issue for the &lt;strong&gt;EU&lt;/st... more &lt;p&gt;Access to marine data is a key issue for the &lt;strong&gt;EU&lt;/strong&gt; &lt;strong&gt;Marine Strategy Framework Directive&lt;/strong&gt; and the &lt;strong&gt;EU&lt;/strong&gt; &lt;strong&gt;Marine Knowledge 2020 agenda &lt;/strong&gt;and includes the &lt;strong&gt;European Marine Observation and Data Network (EMODnet)&lt;/strong&gt; initiative. EMODnet aims at assembling European marine data, data products and metadata from diverse sources in a uniform way.&lt;/p&gt;&lt;p&gt;The EMODnet Bathymetry project is active since 2008 and has developed Digital Terrain Models (DTM) for the European seas, which are published at a regular interval, each time improving quality and precision, and expanding functionalities for viewing, using, and downloading. The DTMs are produced from survey and aggregated data sets that are referenced with metadata adopting the SeaDataNet Catalogue services. SeaDataNet is a network of major oceanographic data centres around the European seas that manage, operate and further develop a pan-European infrastructure for marine and ocean data management. The latest EMODnet Bathymetry DTM release also includes Satellite Derived Bathymetry and has a grid resolution of 1/16 arcminute (circa 125 meters), covering all European sea regions. Use has been made of circa 9400 gathered survey datasets, composite DTMs and SDB bathymetry. Catalogues and the EMODnet DTM are published at the dedicated EMODnet Bathymetry portal including a versatile DTM viewing and downloading service.&amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;As part of the expansion and innovation, more focus has been directed towards bathymetry for near coastal waters and coastal zones. And Satellite Derived Bathymetry data have been produced and included to fill gaps in coverage of the coastal zones. The Bathymetry Viewing and Download service has been upgraded to provide a multi-resolution map and including versatile 3D viewing. Moreover, best-estimates have been determined of the European coastline for a range of tidal levels (HAT, MHW, MSL, Chart Datum, LAT), thereby making use of a tidal model for Europe. In addition, a Quality Index layer has been formulated with indicators derived from the source data and which can be queried in the The Bathymetry Viewing and Download service. Finally, extra functonality has been added to the mechanism for downloading DTM tiles in various formats and special high-resolution DTMs for interesting areas. &amp;#160;&lt;/p&gt;&lt;p&gt;This results in many users visiting the portal, browsing the DTM Viewer, downloading the DTM tiles and making use of the OGC Web services for using the EMODnet Bathymetry in their applications.&lt;/p&gt;&lt;p&gt;The presentation will highlight key details of the EMODnet Bathymetry DTM production process and the Bathymetry portal with its extensive functionality.&lt;/p&gt;
This paper tackles the problem of generating world-scale multi-resolution triangulated irregular ... more This paper tackles the problem of generating world-scale multi-resolution triangulated irregular networks optimized for web-based visualization. Starting with a large-scale high-resolution regularly gridded terrain, we create a pyramid of triangulated irregular networks representing distinct levels of detail, where each level of detail is composed of small tiles of a fixed size. The main contribution of this paper is to redefine three different state-of-the-art 3D simplification methods to efficiently work at the tile level, thus rendering the process highly parallelizable. These modifications focus on the restriction of maintaining the vertices on the border edges of a tile that is coincident with its neighbors, at the same level of detail. We define these restrictions on the three different types of simplification algorithms (greedy insertion, edge-collapse simplification, and point set simplification); each of which imposes different assumptions on the input data. We implement at...
An assessment of ocean depth knowledge underneath commercial airline routes shows just how much o... more An assessment of ocean depth knowledge underneath commercial airline routes shows just how much of the seafloor remains "terra incognita."
Surveying around volcanic ocean islands with sonars has recovered important information on giant ... more Surveying around volcanic ocean islands with sonars has recovered important information on giant landslides, faults and primary volcanic features, but efforts so far have largely been unable to image shallow water coastal areas because of vessel safety. Here we report surveying with a Reson 8160 multibeam sonar aboard a shallow draft research vessel, R/V Arquipelago, which enabled us to survey
Automatic cleaning of MultiBeam EchoSounder (MBES) bathymetric datasets is a critical issue in da... more Automatic cleaning of MultiBeam EchoSounder (MBES) bathymetric datasets is a critical issue in data processing especially with the objective of nautical charting. A number of approaches have already been investigated in order to provide solution in views of operationally reaching this still challenging problem. This paper aims at providing a comprehensive and structured overview of existing contributions in the literature. For this purpose, a taxonomy is proposed to categorize the whole set of automatic and semi-automatic methods addressing MBES data cleaning. The non-supervised algorithms that compose the majority of the methods developed in the hydrographic field, are mainly described according to both the features of the bathymetric data and the type of outliers to detect. Based on this detailed review, past and future developments are discussed in light of both implementation and test on datasets and metrics used for performances assessment.
An iterative Extended Kalman Filter (EKF) approach is proposed to recover a regional set of topog... more An iterative Extended Kalman Filter (EKF) approach is proposed to recover a regional set of topographic heights composing an undersea volcanic mount by the successive combination of large numbers of gravity measurements at sea surface using altimetry satellite-derived grids and taking the error uncertainties into account. The integration of the non-linear Newtonian operators versus the radial and angular distances (and its first derivatives) enables the estimation process to accelerate and requires only few iterations, instead of summing Legendre polynomial series or using noise-degraded 2D-FFT decomposition. To show the effectiveness of the EKF approach, we apply it to the real case of the bathymetry around the Great Meteor seamount in the Atlantic Ocean by combining only geoid height/free-air anomaly datasets and using ship-track soundings as reference for validation. Topography of the Great Meteor seamounts structures are well-reconstructed, especially when regional compensation ...
<p>The AGOSTA project initially proposed by our team and lately funded by CNES TOSCA consis... more <p>The AGOSTA project initially proposed by our team and lately funded by CNES TOSCA consists of developing efficient approaches to restore seafloor shape (or bathymetry), as well as lithospheric parameters such as the crust and elastic thicknesses, by combining different types of observations including gravity gradient data. As it is based on the second derivatives of the potential versus the space coordinates, gravity gradiometry provides more information inside the Earth system at short wavelengths. The GOCE mission has measured the gravity gradient components of the static field globally and give the possibility to detect more details on the structure of the lithosphere at spatial resolutions less than 200 km. We propose to analyze these satellite-measured gravity tensor components to map the undersea relief more precisely than using geoid or vertical gravity previously considered for this purpose. Inversion of vertical gravity gradient data derived from the radar altimetry technique also offers the possibility to reach greater resolutions (at least 50 km) than the GOCE mission one. The seafloor topography estimates are tested in areas well-covered by independent data for validation, such as around the Great Meteor guyot [29&#176;57&#8242;10.6&#8243;N, 28&#176;35&#8242;31.3&#8243;W] and New England seamount chain [37&#176;24&#8242;N 60&#176;00&#8242;W, 120&#176; 10' 30.4" W] in the Atlantic Ocean as well as the Acapulco seamount [13&#176; 36' 15.4" N, 120&#176; 10' 30.4" W] in the Central Pacific.</p>
Morphology and movements of sand dunes are studied using repeated high-resolution bathymetric dat... more Morphology and movements of sand dunes are studied using repeated high-resolution bathymetric data in areas where banner banks approach the shore. Two sites in the Bristol Channel were selected for their contrasting environments. The Helwick Sands is characterised by deeper water-depths, stronger wave climates and weaker tidal currents than the Nash Sands. At the Helwick, migrations of the dunes were measured ranging between 21 and 109 hlv"1. Dunes crossing its crest and connecting despite opposite direction of migration on either flank were observed. This geometry is interpreted to be the result of the strong wave climate coupled with a nearly rectilinear tidal flow, which are leading to dune crests extension. A morphometric study of the sand dunes has revealed the tendency for the dunes to flatten in shallow water, which can also be attributed to the effect of the waves. At the Nash, strong currents and breaking waves have created a strong crestal escarpment. Dune migration r...
&lt;p&gt;Access to marine data is a key issue for the &lt;strong&gt;EU&lt;/st... more &lt;p&gt;Access to marine data is a key issue for the &lt;strong&gt;EU&lt;/strong&gt; &lt;strong&gt;Marine Strategy Framework Directive&lt;/strong&gt; and the &lt;strong&gt;EU&lt;/strong&gt; &lt;strong&gt;Marine Knowledge 2020 agenda &lt;/strong&gt;and includes the &lt;strong&gt;European Marine Observation and Data Network (EMODnet)&lt;/strong&gt; initiative. EMODnet aims at assembling European marine data, data products and metadata from diverse sources in a uniform way.&lt;/p&gt;&lt;p&gt;The EMODnet Bathymetry project is active since 2008 and has developed Digital Terrain Models (DTM) for the European seas, which are published at a regular interval, each time improving quality and precision, and expanding functionalities for viewing, using, and downloading. The DTMs are produced from survey and aggregated data sets that are referenced with metadata adopting the SeaDataNet Catalogue services. SeaDataNet is a network of major oceanographic data centres around the European seas that manage, operate and further develop a pan-European infrastructure for marine and ocean data management. The latest EMODnet Bathymetry DTM release also includes Satellite Derived Bathymetry and has a grid resolution of 1/16 arcminute (circa 125 meters), covering all European sea regions. Use has been made of circa 9400 gathered survey datasets, composite DTMs and SDB bathymetry. Catalogues and the EMODnet DTM are published at the dedicated EMODnet Bathymetry portal including a versatile DTM viewing and downloading service.&amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;As part of the expansion and innovation, more focus has been directed towards bathymetry for near coastal waters and coastal zones. And Satellite Derived Bathymetry data have been produced and included to fill gaps in coverage of the coastal zones. The Bathymetry Viewing and Download service has been upgraded to provide a multi-resolution map and including versatile 3D viewing. Moreover, best-estimates have been determined of the European coastline for a range of tidal levels (HAT, MHW, MSL, Chart Datum, LAT), thereby making use of a tidal model for Europe. In addition, a Quality Index layer has been formulated with indicators derived from the source data and which can be queried in the The Bathymetry Viewing and Download service. Finally, extra functonality has been added to the mechanism for downloading DTM tiles in various formats and special high-resolution DTMs for interesting areas. &amp;#160;&lt;/p&gt;&lt;p&gt;This results in many users visiting the portal, browsing the DTM Viewer, downloading the DTM tiles and making use of the OGC Web services for using the EMODnet Bathymetry in their applications.&lt;/p&gt;&lt;p&gt;The presentation will highlight key details of the EMODnet Bathymetry DTM production process and the Bathymetry portal with its extensive functionality.&lt;/p&gt;
This paper tackles the problem of generating world-scale multi-resolution triangulated irregular ... more This paper tackles the problem of generating world-scale multi-resolution triangulated irregular networks optimized for web-based visualization. Starting with a large-scale high-resolution regularly gridded terrain, we create a pyramid of triangulated irregular networks representing distinct levels of detail, where each level of detail is composed of small tiles of a fixed size. The main contribution of this paper is to redefine three different state-of-the-art 3D simplification methods to efficiently work at the tile level, thus rendering the process highly parallelizable. These modifications focus on the restriction of maintaining the vertices on the border edges of a tile that is coincident with its neighbors, at the same level of detail. We define these restrictions on the three different types of simplification algorithms (greedy insertion, edge-collapse simplification, and point set simplification); each of which imposes different assumptions on the input data. We implement at...
An assessment of ocean depth knowledge underneath commercial airline routes shows just how much o... more An assessment of ocean depth knowledge underneath commercial airline routes shows just how much of the seafloor remains "terra incognita."
Surveying around volcanic ocean islands with sonars has recovered important information on giant ... more Surveying around volcanic ocean islands with sonars has recovered important information on giant landslides, faults and primary volcanic features, but efforts so far have largely been unable to image shallow water coastal areas because of vessel safety. Here we report surveying with a Reson 8160 multibeam sonar aboard a shallow draft research vessel, R/V Arquipelago, which enabled us to survey
Automatic cleaning of MultiBeam EchoSounder (MBES) bathymetric datasets is a critical issue in da... more Automatic cleaning of MultiBeam EchoSounder (MBES) bathymetric datasets is a critical issue in data processing especially with the objective of nautical charting. A number of approaches have already been investigated in order to provide solution in views of operationally reaching this still challenging problem. This paper aims at providing a comprehensive and structured overview of existing contributions in the literature. For this purpose, a taxonomy is proposed to categorize the whole set of automatic and semi-automatic methods addressing MBES data cleaning. The non-supervised algorithms that compose the majority of the methods developed in the hydrographic field, are mainly described according to both the features of the bathymetric data and the type of outliers to detect. Based on this detailed review, past and future developments are discussed in light of both implementation and test on datasets and metrics used for performances assessment.
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