A series of six photos showing the launch of the Hugin AUV. A newly-developed AUV, owned and operated by C&C Technologies, was used to complete bathymetric surveys at four sites for this project Click image for larger view and image credit.
Closer and Closer to Fine
June 10, 2007
Harry Roberts
Louisiana State University
27° 38.41N
88° 21.51W
As Bill Shedd indicated in yesterday’s log, we recognized the need to move beyond reconnaissance-level bathymetry provided by 3-D seismic data to a higher resolution image of submarine topography associated with our key sampling sites. To acquire these data we contracted the use of an autonomous underwater vehicle (AUV) from C&C Technologies of Lafayette, Louisiana. Their AUV, the Hugin, was the first to be used in the Gulf of Mexico. It was developed in response to needs of the oil and gas industry for pipeline surveys and seafloor-engineering studies as exploration and production moved from the upper continental slope to the deeper parts of the northern Gulf. At water depths beyond about 1000m older towed vehicles became difficult to locate in the water column and turns in a survey grid were very time-consuming because of long cable lengths. In contrast, a free-swimming vehicle like Hugin was relatively more efficient as water depths increased. In addition to high-resolution swath bathymetry, the Hugin was also designed to collect side-scan sonar data and subbottom profiles.
The AUV data was used to complete this high resolution bathymetric map of site AT 340. Several of the habitats visited with the ALVIN submersible during last summerís cruise are located on the map. We are conducting detailed sampling at may of these habitats during this cruise. Click image for larger view and image credit.
In data acquisition mode, the Hugin “flies” at a constant depth above the bottom and travels along predetermined tracks programmed into the system before leaving the support ship. Our data were acquired by a new generation of C&C Technologies AUVs, the C-Surveyor II. Based on last year’s Alvin work, four sites located in the eastern, central, and western sectors of the northern Gulf’s deep slope were selected for detailed bathymetric surveys. These four sites were chosen from 10 sites originally determined from 3-D seismic data and verified as seeps sites by a camera survey conducted prior to the ALVIN dives. Each of the four AUV-surveyed sites had hydrocarbon seepage and well-developed chemosynthetic communities. We selected these sites because the AUV-resolution bathymetry would be incredibly beneficial in the development of our detailed sampling plans for the Jason dives on this cruise.
The high-resolution bathymetry produced by the C-Surveyor II is being used in this year’s project as an underlay map for plotting Jason ROV tracks and our sample stations. Having this high-resolution bathymetry has provided information on seafloor configuration that has helped significantly in the planning and recording of sampling activities of all types. Within this excellent framework of AUV-derived bathymetry, the Jason is also making it’s own swath bathymetry maps of localized areas that have high scientific value. The Jason has a very high-resolution swath bathymetry mapping system onboard that can resolve features on the seafloor of just a few tens of centimetersrelief. Boulders and dense communities of tube worm bushes can be resolved with this mapping technology. So, the scientists on this cruise have three levels of bathymetry at their disposal to support their studies; reconnaissance-level bathymetry from the 3-D seismic data, AUV bathymetry for navigating within the site and locating sample sites, and Jason ROV bathymetry for detailed spatial studies of communities and their surrounding environments.
