Roberto J. Anima
John L. Chin
David P. Finlayson
Mary L. McGann
Florence L. Wong
2007
2-m resolution backscatter grid of Tomales Bay, California (TOMALESAMPG)
October 11, 2007
map
USGS Open-File Report
USGS OFR 2007-xxxx
Menlo Park, California
U.S. Geological Survey
<URL:http://pubs.usgs.gov/of/2008/1237/>
The SWATHplus interferometric sidescan stores backscatter amplitude
with each bathymetric sounding. This amplitude data can be plotted to
produces an acoustic image of the sea floor. Cell values in the image
represent the relative strength of the acoustic signal returned
(backscattered) to the transducer off of the sea bed. A cell value
equal to 1.0 is an average strength return, cell values above 1.0 are
relatively stronger than average; values less than 1 are below average
strength returns.
The Tomales Bay backscatter amplitude grid
is composed of data from two
interferometric sidescansonar surveys collected in November
2004 and November 2005 (USGS activities F-1-04-TB,
F-2-05-TB).
This metadata record describes the Tomales Bay grid exported as
1. ESRI ASCII grid format (includes nodata -9999 values)
> ncols 5442
> nrows 7069
> xllcorner 501421
> yllcorner 4218273
> cellsize 2
> NODATA_value -9999
> -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999
> -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999
> -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 -9999 0 0 0 0 0 0
2. x-y (decimal degrees) and z (strength of acoustic return relative to
mean value) data (nodata excluded).
> -122.98290,38.23969,0.000
> -122.98288,38.23969,0.000
> -122.98286,38.23969,0.000
> -122.98284,38.23969,0.000
> -122.98282,38.23969,0.000
> -122.98280,38.23969,0.000
> -122.98278,38.23969,0.000
> -122.98292,38.23967,1.315
> -122.98290,38.23967,1.346
These data are intended for science researchers, students, policy
makers, and the general public. The data can be
used with geographic information systems (GIS) software
to display geologic and oceanographic information.
Additional information about the field activities from
which this data set was derived are available online at
>http://walrus.wr.usgs.gov/infobank/f/f104tb/html/f-1-04-tb.meta.html
>http://walrus.wr.usgs.gov/infobank/f/f205tb/html/f-2-05-tb.meta.html
Any use of trade, product, or firm names is for descriptive purposes
only and does not imply endorsement by the
U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata
file is intended to document the data set in nonproprietary form,
as well as in ArcInfo format, this metadata file may include some
ArcInfo-specific terminology.
2006
Ground Condition
None Planned
-122.98379025
-122.85938895
38.23970089
38.11219761
None
coastal geology
bathymetry
sidescan
interferometric sidescan
ISO 19115 Topic Category
environment
geoscientificInformation
oceans
Geographic Names Information System
Tomales Bay, California
Inverness Ridge, California
San Andreas Fault, California
Avalis Beach, California
Lawsens Landing, California
Pelican Point, California
Blakes Landing, California
Marconi, California
Hearts Desire Beach, California
Millerton Point, California
Inverness, California
Lagunitas Creek, California
Toms Point, California
White Gulch, California
Tomales Beach, California
Marshall Beach, California
Lairds Landing, California
Cypress Grove, California
Reynolds, California
California
USA
GEOnet Names Server
north Pacific Ocean
None
These data are not to be used for navigation.
Florence L. Wong
United States Geological Survey (USGS)
Coastal and Marine Geology (CMG)
Geologist, GIS Coordinator
mailing and physical address
USGS, MailStop 999, 345 Middlefield Road
Menlo Park
CA
94025-3561
USA
(650) 329-5327
(650) 329-5190
fwong@usgs.gov
http://pubs.usgs.gov/of/2008/1237/images/tomalesg.jpg
preview image of report
gif or jpg
SunOS, 5.8, sun4u UNIX
ArcInfo version 9.1
The advertised accuracy of the SWATHplus system in shallow
waters is better than IHO S44 Special Order, but a total
propagation error model has not been developed for the USGS
system used in these surveys so the true error in both
position and elevation is unknown.
Not applicable for raster data.
Complete.
See Attribute_Accuracy_Report.
Swath bathymetry and backscatter.
Swath bathymetry and backscatter for the northern and central portions of
Tamales Bay (cruise F-1-04-TB and F-2-05-TB) were collected
using a pole-mounted, SEA Inc., 234 kHz, SWATHplus
interferometric sidescan sonar system. Attitude
compensation and vessel positioning were provided by a
CodaOctopus F180 attitude and positioning system. Sound
velocity profile measurements were collected with an
Applied Micro Systems, SvPlus 3472.
The horizontal datum of the surveys was established by
differential GPS using the WGS84 ellipsoid.
Raw bathymetry and amplitude data were collected using the
Swath Processor software provided with the sonar system.
The first step in the acoustic data processing
applies an empirical gain function to
the raw soundings to counteract systematic artifacts observed in the
amplitude values that are associated with variable slant-ranges and
grazing angles. The procedure normalizes the raw amplitude values with
the mean amplitude of all soundings in the survey collected at similar
ranges and depths from the transducer. Second, the normalized
amplitude values are gridded using the Generic Mapping Tools (GMT).
Third, the amplitude grid is converted to ESRI ASCII grid format,
loaded into ArcGIS and the two survey years are mosaiced together.
2007
First draft of metadata created by curator using
FGDCMETA.AML ver. 1.35 08/02/2000 on ArcInfo data set
/arcdata/sonar/tomales/tomalesampg
20071011
Raster
Grid Cell
7069
5442
Universal Transverse Mercator
10
0.9996
-123.0
0.0
500000
0
coordinate pair
2.0
2.0
Meters
WGS84
WGS84
6378206.4
294.98
>
>TOMALESAMPG.STA:
>
> backscatter amplitude relative to a mean value of 1.0
>
>COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
> 1 MIN 8 15 F 3
> 9 MAX 8 15 F 3
> 17 MEAN 8 15 F 3
> 25 STDV 8 15 F 3
>
> MIN MAX MEAN STDV
> 0.000 1.768 1.003 0.073
>
none
United States Geological Survey (USGS)
Coastal and Marine Geology (CMG)
Florence L. Wong
Geologist, GIS Coordinator
mailing and physical address
USGS, MailStop 999, 345 Middlefield Road
Menlo Park
CA
94025-3561
USA
(650) 329-5327
(650) 329-5190
fwong@usgs.gov
USGS OFR 04-xxx
Please recognize the U.S. Geological Survey (USGS) as the source of
this information.
Although these data have been used by the U.S. Geological Survey,
U.S. Department of the Interior, no warranty expressed or implied
is made by the U.S. Geological Survey as to the accuracy of the
data.
The act of distribution shall not constitute any such warranty,
and no responsibility is assumed by the U.S. Geological Survey in
the use of this data, software, or related materials.
Compressed file including Arcinfo grid and metadata.
9.2
Arcinfo ASCII grid
windows winzip or unix gunzip
15 MB
http://pubs.usgs.gov/of/2008/1237/
none
20071011
200710
United States Geological Survey (USGS)
Coastal and Marine Geology (CMG)
Florence L. Wong
Geologist, GIS Coordinator
mailing and physical address
USGS, MailStop 999, 345 Middlefield Road
Menlo Park
CA
94025-3561
USA
(650) 329-5327
(650) 329-5190
fwong@usgs.gov
FGDC Content Standards for Digital Geospatial Metadata ("CSDGM version 2")
FGDC-STD-001-1998
none
none