1-m resolution bathymetry collected in Coyote Creek and Alviso Slough in April 2015.
Projection = UTM, zone 10 in meters,
Horizontal Datum = NAD83 (CORS96),
Vertical Datum = MLLW, all units in meters.
The surveys extend east from Calaveras Point along Coyote Creek to the railroad bridge,
along Alviso Slough to the town of Alviso (just over 7 km), and along the 3.7 km of Guadalupe
Slough closest to the San Francisco Bay, California.
Additional information about the field activities from which these
data were derived is available online at:
Any use of trade, product, or firm names is for descriptive purposes only
and does not imply endorsement by the U.S. Government.
Theme_Keyword_Thesaurus:None Theme_Keyword:U.S. Geological Survey Theme_Keyword:USGS Theme_Keyword:Coastal and Marine Geology Program Theme_Keyword:CMGP Theme_Keyword:Pacific Coastal and Marine Science Center Theme_Keyword:PCMSC
Place_Keyword_Thesaurus:Geographic Names Information System (GNIS) Place_Keyword:State of California Place_Keyword:San Francisco Bay Place_Keyword:Alameda County Place_Keyword:Santa Clara County Place_Keyword:Alviso Place_Keyword:Coyote Creek Place_Keyword:Alviso Slough Place_Keyword:Guadalupe Slough
USGS-authored or produced data and information are in the public
domain from the U.S. Government and are freely redistributable with
proper metadata and source attribution.
Please recognize and acknowledge the U.S. Geological Survey as the
originator of the dataset and in products derived from these data.
This information is not intended for navigational purposes.
Contact_Organization:USGS Pacific Coastal and Marine Science Center Contact_Person:Amy Foxgrover
Address_Type:mailing and physical Address:2885 Mission Street City:Santa Cruz State_or_Province:CA Postal_Code:95060 Country:USA
Originator:Amy C. Foxgrover Originator:Bruce E. Jaffe Originator:Gerald T. Hovis Originator:Craig A. Martin Originator:James R. Hubbard Originator:Manoj R. Samant Originator:Steve M. Sullivan Publication_Date:2007 Title:2005 Hydrographic Survey of South San Francisco Bay, California Series_Information:
Transforming positions and velocities between the International Terrestrial Reference
Frame of 2000 and North American Datum of 1983
Series_Name:Journal article Issue_Identification:Journal of Surveying Engineering, v. 130, no. 2
These bathymetric data have not been independently verified for accuracy.
All bathymetric values are derived from the same instruments and processing workflow.
The raw bathymetry data were filtered in SEA Swath Processor and imported into CARIS HIPS and SIPS for post-processing.
Within CARIS a swath angle BASE (Bathymetric with Associated Statistical Error) surface was created at 1 m resolution and the
subset editor used to manually eliminate any remaining outliers or artifacts. The average depth within each 1 by 1 m cell was exported
as an ASCII text file and imported into Surfer for interpolation using a linear kriging algorithm with a 1-simga nugget of 0.05 m and a
2 by 2 m search radius. The resultant grid was exported to ESRI ArcMap software for display.
Uncertainty in the horizontal position of each sounding is a function of the total uncertainty propagated through
each of the following component instruments: 1) base station GPS, 2) vessel GPS, 3) inertial
motion unit (IMU), 4) water sound velocity model, and 5) beam spreading in the water column. Assuming no
systematic errors in the measurement instruments themselves, beam spreading is the dominate source
of positional uncertainty. The 1-degree sonar beam of the SWATHplus-M results in horizontal uncertainty ranging
from 0.10 m at 10 m slant range, to about 0.45 m at 50 m slant range.
After filtering the data to remove obvious outliers, the standard deviation of the remaining sounding elevations
was calculated for each 1 m by 1 m cell (each containing 19 soundings on average) in CARIS. The mean
of the standard deviation for all cells in the survey is 0.06 m.
Additional uncertainty associated with the vertical datum conversion from NAVD88 to MLLW has not been
This 2015 field activity collected bathymetric data in San Francisco Bay.
Bathymetric surveys were conducted using a 234.5 kHz SEA (Systems Engineering and Assessment Ltd)
SWATHplus-M phase-differencing sidescan sonar. The sonar was pole-mounted on the 34-foot USGS
mapping vessel R/V Parke Snavely, and affixed to a hull brace. GPS position data were passed through
an Applanix Position and Motion Compensation System for Marine Vessels POS/MV inertial measurement
unit (IMU) to the sonar hardware and data-collection software.
Sonar heads, GPS antennae, and the IMU were surveyed in place to a common reference frame with a
Geodimeter 640 Total Station. The R/V Snavely was outfitted with three networked workstations
and a navigation computer for use by the captain and survey crew for data collection and initial
An Applanix Position and Motion Compensation System for Marine Vessels (POS/MV) was used to accurately determine the
survey vessel's position. The POS/MV utilizes Global Navigation Satellite System (GNSS) data in combination with angular
rate and acceleration data from the IMU and heading data from the GPS Azimuth Measurement Systems (GAMS) to produce accurate
position and orientation information through a virtual network of base stations. As opposed to receiving high-accuracy Real-Time
Kinematic (RTK) corrections, the POS records raw inertial and GNSS data while surveying, which is later refined through
post processing to incorporate publicly available GPS data from nearby base stations. During post processing the POS/MV
data is run through POSPac software to produce a Smoothed Best Estimate of Trajectory (SBET) file, which is then imported
back into Swath Processor to produce high-accuracy positions relative to the WGS84 ellipsoid. The RMS results from our
POS/MV surveys show positional errors of less than 5 cm in X, Y, and Z.
Sound velocity measurements were collected continuously with an Applied Micro Systems Micro SV deployed
on the transducer frame for real-time sound velocity adjustments at the transducer-water interface. The Micro
SV is accurate to +/- 0.03 m/s. In addition, sound velocity profiles (SVP) were collected with an Applied Micro
Systems, SvPlus 3472. This instrument provides time-of-flight sound-velocity measurements by using invar rods
with a sound-velocity accuracy of +/- 0.06 m/s, pressure measured by a semiconductor bridge strain gauge to an
accuracy of 0.15 percent (Full Scale) and temperature measured by thermistor to an accuracy of 0.05 degrees
Celsius (Applied Microsystems Ltd., 2005).
GPS data and measurements of vessel motion (heave, pitch, and roll) are combined in the POS/MV hardware to
produce a high-precision vessel attitude packet. This packet is transmitted to the Swath Processor acquisition
software in post-processing and combined with instantaneous sound velocity measurements at the transducer
head before each ping. Up to 20 pings per second are transmitted with each ping consisting of 2048 samples
per side (port and starboard). The returned samples are projected to the seafloor using a ray-tracing algorithm
working with the previously measured sound velocity profiles in SEA Swath Processor (version 3.7.17). A
series of statistical filters are applied to the raw samples that isolate the seafloor returns from other
uninteresting targets in the water column. Finally, the processed data are stored line-by-line in both raw (.sxr)
and processed (.sxp) trackline files.
The raw bathymetry data were filtered in SEA Swath Processor (version 3.7.17) and imported into
CARIS HIPS and SIPS (version 8.1) for post-processing. Within CARIS a swath angle BASE
(Bathymetric with Associated Statistical Error) surface was created at 1 m resolution and the
subset editor used to manually eliminate any remaining outliers or artifacts. The average depth
within each 1 by 1 m cell was exported as an ASCII text file and imported into Surfer (version 10)
for interpolation using a linear kriging algorithm with a 1-simga nugget of 0.05 m and a 2 by 2 m
search radius. The resultant grid was exported to ESRI ArcMap (version 10.2.2) for display and
further analyses. The entire survey was shoaled by 7 cm to account for a combination of biases
resulting from changes in the boat instrumentation and configurations that occurred since the
initial survey was collected in 2010.
To convert the bathymetry from WGS84 ellipsoid heights to the tidal datum of MLLW
the data were first transformed from WGS84(ITRF2000) to the NAD83(CORS96) ellipsoid
using a 14-point Helmert transformation described by Soler and Snay (2004) using the
command line tool CS2CS in the Proj4 library (http://trac.osgeo.org/proj/). A fixed
Geoid09 offset of -32.62 m was then applied to convert the NAD83 ellipsoid heights to
orthometric heights NAD83(CORS96)/NAVD88. The orthometric NAVD88 elevations were
converted to MLLW using the conversions provided by the CO-OPS division of NOAA for a
2005 bathymetric survey of South San Francisco Bay (Foxgrover and others, 2007).
These data are available in both X,Y,Z text file format and ESRI ASCII Raster format.
Both formats are contained in a single zip file (Apr_2015.zip), which also includes
CSDGM FGDC-compliant metadata.
Unless otherwise stated, all data, metadata and related materials are considered to
satisfy the quality standards relative to the purpose for which the data were collected.
Although these data and associated metadata have been reviewed for accuracy and completeness
and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or
implied is made regarding the display or utility of the data on any other system or for general
or scientific purposes, nor shall the act of distribution constitute any such warranty.
where xxx is a number, and the keyword nodata_value is optional and defaults to -9999. Row 1 of the data is
at the top of the grid, row 2 is just under row 1 and so on. The nodata_value is the value in the ASCII file to
be assigned to those cells whose true value is unknown. In the grid they will be assigned the keyword NODATA.
Cell values are delimited by spaces. No carriage returns are necessary at the end of each row in the grid
(although they are included in this case). The number of columns in the header is used to determine when a
new row begins. The number of cell values is equal to the number of rows times the number of columns.