United States Geological Survey, Menlo Park, California. Chief Scientist: Guy Cochrane. Seismic and Sidescan Sonar and Video data (YoNav, Kleinsidescan, underwatercamera) of field activity B-1-98-SC in Santa Barbara Coast and Channel Islands from 06/14/1998 to 06/29/1998
Location
Santa Barbara Coast and Channel Islands
Summary
We used the R/V Ballena, owned by the Channel Islands National Marine Sanctuary, for our geophysical surveying. Combined sidescan-sonar imaging, seismic reflection profiling, and towed bottom camera work began on June 15 after a day of mobilization, and ended June 26 with one day of demobilization. Data was collected in nearshore waters, here defined as 0 to 100 meters in depth. Two areas were surveyed in 1998, a 59 square km area north of Anacapa Island, and a 113 square km area surrounding the Big Sycamore Canyon Reserve, on the California coast, northwest of Pt. Dume. Approximately 6 hours of bottom video was recorded in each of the two areas for groundtruthing the sidescan.The geophysical surveying done in this and future years will be combined with existing population studies, sediment sampling, ROV, submersible, and bottom video camera observations to better understand benthic habitat - faunal relationships. Navigation Systems - The 1998 survey was navigated with a Leica Differential Global Positioning System (DGPS) which provided a ship position with accuracy of 1-5 m in DGPS mode. At times during the cruise differential signal was interrupted. In non-differential mode, the receiver provided a position with 30-50 m accuracy. A KVH Industries Inc. azimuth digital gyro-compass provided ship headings with 0.5 degree accuracy. Navigation data were recorded using Yo-Nav version 1.19 (Gann, 1992). The sidescan fish is towed approximately 20 m above the seafloor. The distance behind the ship of the fish was not known during this survey and must be estimated when the data is processed in order to produce the sidescan image mosaics. Sidescan Surveying System - A Klein 2000 sidescan system was used for geophysical surveying. The unit features 8 channels of processed data, 7 subsurface from the towfish (5 sonar and 2 instrumentation) and 1 surface (external analog input). Two sonar channels each were devoted to 100 KHz and 500 KHz sidescan data and a fifth sonar channel was used for 4 KHz subbottom profiling. The resolution of the profiler data is approximately 0.15 m of sub-bottom thickness (penetration of tens of meters is typical in unconsolidated sediment). A Triton Elics Isis brand side-scan data recording system was used on the cruise. The Isis system simultaneously records 5 channels of data; port and starboard 100 KHz side-scan data, port and starboard 500 KHz side-scan data, and profiler data. Side-scan data shown in this report are 100 KHz data. Typically, 2048 samples were recorded per channel over a swath width of 400 m yielding a pixel size of 0.1 m of seafloor area for the side-scan data.
Info derived
2048 samples were recorded per channel over a swath width of 400 m yielding a pixel size of 0.1 m of seafloor area for the side-scan data.
Comments
Associated cruises in southern California: B-1-98-SC B-1-99-SC B-2-99-SC M-1-99-SC M-1-00-SC J-1-02-SC M-1-02-SC M-1-03-SC S-5-04-SC June 26, 1998 TIDBIT FROM THE CHANNEL ISLANDS This from Guy Cochrane, via phone mail from the R/V Ballena: "Shot 40 sq km of side-scan with the Klein system off the north side of Anacapa Island, working with Channel Islands Marine Sanctuary people and the National Marine Fisheries Service. Weve also done a day and a half of bottom video using Hanks camera sled, so we have about two hours of video tape. Weve had really great weather. Conditions have been perfect for both side-scan and bottom video. Mike Boyle and I are doing okay." July 10, 1998 CHANNEL ISLANDS BENTHIC HABITATS CRUISE Mike Boyle and I finished the two-week Channel Islands/Santa Barbara benthic habitats cruise on Saturday, June 27, and off-loaded on Sunday, June 28. We sidescanned a 40-sq-km area of Anacapa Island and a 60-sq-km area on the coast south of Ventura. Both areas contain state fish reserve areas and are in the Channel Islands National Marine Sanctuary, or the National Park. We also have about 8 hours of bottom video from both areas, thanks to very cooperative weather. We did have some trouble with Differential GPS reception and will try to improve our system prior to returning to the area. Guy Cochrane
Staff information imported from InfoBank
Guy Cochrane (USGS Western Region) - Chief Scientist
Mike Boyle (USGS Western Region) - Electronic Technician
The sidescan sonar image of the nearshore seafloor (0 to 100 m water depths) of the Big Sycamore reserve area was mosaicked from data collected in 1998. A Klein 2000 sidescan system was used for geophysical surveying. A Triton Elics Isis brand side-scan data recording system was used on the cruise. The 1998 survey was navigated with a Leica Differential Global Positioning System (DGPS) which provided a ship position with accuracy of 1-5 m in DGPS mode. At times during the cruise differential signal was interrupted. In non-differential mode, the receiver provided a position with 30-50 m accuracy. A KVH Industries Inc. azimuth digital gyro-compass provided ship headings with 0.5 degree accuracy. Navigation data were recorded using Yo-Nav version 1.19 (Gann, 1992). The sidescan fish was towed approximately 30 m above the seafloor. The distance of the fish behind the ship was not known during this survey and must be estimated when the data are processed in order to produce the sidescan image mosaics. The resolution of the processed data mosaics is 0.2 m. The data are presented here at a resolution of 1 m. This is one of a collection of digital files of a geographic information system of spatially referenced data related to the USGS Coastal and Marine Geology Program Nearshore Benthic Habitat Mapping Project. See <http://walrus.wr.usgs.gov/nearshorehab> for more information.
The sidescan sonar image of the nearshore seafloor (0 to 100 m water depths) of the Big Sycamore reserve area was mosaicked from data collected in 1998. The resolution of the processed data mosaics is 0.2 m. The data are presented here at a resolution of 1 m. This is one of a collection of digital files of a geographic information system of spatially referenced data related to the USGS Coastal and Marine Geology Program Nearshore Benthic Habitat Mapping Project. See <http://walrus.wr.usgs.gov/nearshorehab> for more information.
