The Gulf of the Farallones: Sidescan-Sonar ImageryEntry ID: USGS_OFR_2004_1082
Abstract: In 1989, the U.S. Geological Survey (USGS) began a major geologic and
oceanographic investigation of the Gulf of the Farallones National Marine
Sanctuary continental shelf system, designed to evaluate and monitor human
impacts on the marine environment (Karl and others, 2002). The study region is
located off the central California coast, adjacent to San Francisco Bay and
encompasses the Gulf of ... Farallones Marine Sanctuary. Geologic mapping of this
area included the use of various remote sensing and sampling techniques such as
shallow sub-bottom profiling, sidescan-sonar and bathymetric mapping, gravity
core and grab sampling, and photography. These data were used to define the
surficial sediment distribution, underlying structure and sea floor morphology
of the study area.
The primary focus of this report is to present a georeferenced, digital
sidescan-sonar mosaic of the study region. The sidescan-sonar data were
acquired with the AMS-120 (120 kHz) sidescan-sonar system during USGS cruise
F9-89-NC. The dataset covers approximately 1000 km² of the continental shelf
between Point Reyes, California and Half Moon Bay, California, extending west
to the continental shelf break near the Farallon Islands. The sidescan-sonar
mosaic displays a heterogenous sea-floor environment, containing outcropping
rock, ripples, dunes, lineations and depressions, as well as flat, featureless
sea floor (Karl and others, 2002). Location of Sidescan-Sonar Mosaic Figure 3.
Outline of the Gulf of Farallones AMS-120 sidescan-sonar study region. These
data, along with sub-bottom interpretation (Chin and others, 1997) and ground
truth data (Maher and others, 1991) define the geologic framework of the
region. The sidescan-sonar mosaic can be used with supplemental remote sensing
and sampling data as a base for future research, helping to define the local
current regime and predominant sediment transport directions and forcing
conditions within the Gulf of Farallones.
[Summary provided by the USGS.]
(Click for Interactive Map)
Data Set Citation
Dataset Originator/Creator: Sweeney, E.M., Danforth, W.W., Karl, H.A., O'Brien, T.F., Schwab, W.C.
Dataset Title: The Gulf of the Farallones: Sidescan-Sonar Imagery
Dataset Series Name: Open File Report 2004-1082
Dataset Release Date: 2004
Dataset Publisher: U.S. Geological Survey
Data Presentation Form: GIS dataOnline Resource: http://pubs.usgs.gov/of/2004/1082/index.htm
Start Date: 1993-01-01Stop Date: 1997-12-31
Quality ATTRIBUTE ACCURACY REPORT: Thematic accuracy was checked using GPS controlled
navigation to representative areas of the coastline. The vector polygon data
was loaded into a field PC and displayed in ArcView software. A tracking
software allowed the analyst to travel to specific points in the data with
precision and to check the type of habitat in the ... field. Sample sites were
selected based on their location and distribution along the coast. No empirical
accuracy statistics were generated.
LOGICAL CONSISTENCY REPORT: Following interpretation and digitization, a Arc
format polygon coverage was produced using the BUILD commands. An editing
process was also conducted to ensure proper polygon labelling and closure.
COMPLETENESS REPORT: All SAV habitat interpretable from aerial imagery was
mapped. No gaps exist in the geographic distribution of the data.
HORIZONTAL POSITIONAL ACCURACY REPORT: Horizontal accuracy meets national map
accuracy standards. This was one of the most important factors in the initial
VERTICAL POSITIONAL ACCURACY REPORT: Vertical accuracy was not tested.
PROCESS DESCRIPTION: Aerial photograhpy acquisition Conventional color (Kodak
Aerochrome 2448) film was acquired over the Maine coast at a nominal scale of
1:12,000. The coast was flown in an incremental fashion in 1993, 1994, 1995,
1996, and 1997. The film was flown according to the environmental parameters
recommended in the C-CAP protocol. The mission specifications included 60%
endlap and 30% sidelap for adjacent lines. A 153mm color corrected lens and
Wild RC10 camera were used to collect the imagery. PROCESS DATE: 1993-1997
PROCESS DESCRIPTION: Photo-Interpretation The duplicated film diapositives were
interpreted monoscopically on a large-format light table. SAV habitat was
annotated on acetate overlays attached to the film. The habitat was assigned to
1 of four density classes based on percent ground coverage by actual eelgrass.
The photography was interpreted by a skilled analyst who is very familiar with
the local environment. GPS controlled field work was used to develop signatures
suitable form mapping. PROCESS DATE: 1993-1997
PROCESS DESCRIPTION: Data Vectorization At the conclusion of the interpretation
process, the diapositives were with overlays attached were placed on the light
table below mylar USGS 7.5 minute quads. The photos were manually fitted to the
USGS map and the habitat polygons were transferred to the quad mylars. Then the
annotated mylar was scanned and an automated vectorization software was used to
capture the linework as ESRI vectors. These vectors were manually edited and a
polygon coverage was built using ArcInfo software. The benthic data is
classified according to the System for Classification of Habitats in Estuarine
and Marine Environments (SCHEME). This system is fully described in
"Development of a System for Classification of Habitats in Estuarine and Marine
Environments (SCHEME) for Florida, Report to U.S. EPA - Gulf of Mexico Program,
Florida Fish and Wildlife Conservation Commission, Florida Marine Research
Institute. Review Draft 12/04/02."
SOURCE INFORMATION - CITATION: James Sewall Inc.. Conventional color metric
aerial photography. 1993. 1. GEOSPATIAL DATA PRESENTATION FORM: map. OTHER
CITATION DETAILS: Aerial photography acquired according to C-CAP protocol.
Coastal Change Analysis Program (C-CAP): Guidance for Regional Implementation.
NMFS Technical Report 123.
SOURCE SCALE DENOMINATOR: 12000.
TYPE OF SOURCE MEDIA: color film diapositives.
BEGINNING TIME: 1993.
ENDING TIME: 1997.
SOURCE CURRENTNESS REFERENCE: Ground Condition.
SOURCE CONTRIBUTION: The aerial photography was used to identify and delineate
SAV habitat. In addition, the photos form the backdrop for certain field
Access Constraints DISTRIBUTION LIABILITY: None
Use Constraints Not for Navigation
Data Set Progress
Distribution Media: ONLINE
Distribution Format: ESRI Arc Export format
Role: TECHNICAL CONTACT
Phone: (843) 740-1200
2234 South Hobson Avenue
Province or State: South Carolina
Postal Code: 29405
Role: DIF AUTHOR
Email: csc at csc.noaa.gov
NOAA Coastal Services Center 2234 South Hobson Avenue
Province or State: SC
Postal Code: 29405-2413
Creation and Review Dates
DIF Creation Date: 2000-04-03
Last DIF Revision Date: 2012-02-23