USGS CMG B-1-98-SC Metadata

Nearshore Benthic Habitats mapping

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.

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.

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. We've also done a day and a half of bottom video using Hank's camera
sled, so we have about two hours of video tape. We've 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

Cochrane, G.R., and Lafferty, K.D., 2000, Activities and Preliminary Results of 
Nearshore Benthic
Habitat Mapping in Southern California, 1998, U.S. Geological Survey Open File 
Report 2000-321:

http://pubs.er.usgs.gov/usgspubs/ofr/ofr00321



Cochrane, G.R., Nasby, N.M., Reid, J.A., Waltenberger, B., and Lee, K.M., 2003, 
Nearshore
Benthic Habitat GIS for the Channel Islands National Marine Sanctuary and 
Southern California State
Fisheries Reserves Volume 1, U.S. Geological Survey Open File Report 
2003-85:

http://pubs.er.usgs.gov/usgspubs/ofr/ofr0385