Estero Bay, California, Acoustic Backscatter (Field Activity ID: S-05-12-SC)

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U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), Santa Cruz, CA.
Publication_Date: 2013
Estero Bay, California, Acoustic Backscatter (Field Activity ID: S-05-12-SC)
Geospatial_Data_Presentation_Form: raster digital data
Series_Name: U.S. Geological Survey Open-File Report
Issue_Identification: 2013-1225
Online_Linkage: <>
Between July 30 and August 09, 2012, scientists from the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), acquired bathymetry and acoustic-backscatter data from Estero Bay, San Luis Obispo, California, under PCMSC Field Activity ID S-05-12-SC. The survey was conducted using the R/V Parke Snavely outfitted with a multibeam sonar system for swath mapping and inertially-aided real-time kinematic navigation equipment for accurate georeferencing. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.
These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems or other software to identify bathymetric features. This information is not intended for navigational purposes.
The URL for USGS field activity S-05-12-SC is <>
Beginning_Date: 20120730
Ending_Date: 20120809
Currentness_Reference: ground condition
Progress: complete
Maintenance_and_Update_Frequency: as needed
West_Bounding_Coordinate: -121.172404
East_Bounding_Coordinate: -120.915074
North_Bounding_Coordinate: 35.520167
South_Bounding_Coordinate: 35.224352
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificInformation
Theme_Keyword: oceans
Theme_Keyword: elevation
Place_Keyword_Thesaurus: Geographic Names Information System (GNIS)
Place_Keyword: State of California
Place_Keyword: San Luis Obispo
Place_Keyword: Estero bay
Place_Keyword: Morro Bay
If physical samples or materials are available, constraints on their on-site access are described in "WR CMG Sample Distribution Policy" at URL: <>
This information is not intended for navigational purposes.
Read and fully comprehend the metadata prior to data use. Uses of these data should not violate the spatial resolution of the data. Where these data are used in combination with other data of different resolution, the resolution of the combined output will be limited by the lowest resolution of all the data.
Acknowledge the U.S. Geological Survey in products derived from these data. Share data products developed using these data with the U.S. Geological Survey.
This database has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document these data in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.
Contact_Organization: USGS Pacific Coastal and Marine Science Center
Contact_Person: Steve R Hartwell
Contact_Position: Geologist
Address_Type: physical address
Address: U.S. Geological Survey
Address: 400 Natural Bridges Drive
City: Santa Cruz
State_or_Province: CA
Postal_Code: 95060
Country: USA
Contact_Voice_Telephone: (831) 460-7814
Contact_Facsimile_Telephone: (831) 427-4748

This bathymetric data has not been independently verified for accuracy.
All bathymetric values are derived from the same instruments and processing workflow.
The 2012 mapping mission (U.S. Geological Survey (USGS) Field Activity ID: S-05-12-SC) collected high-resolution bathymetry and coregistered acoustic backscatter of outer Estero Bay, California. The survey was completed in 11 days, from July 30 to August 9, 2012, and consisted of 117 survey lines covering approximately 165 sq km in elevations ranging from about -45 m to -250 m relative to NAVD88. The survey extends from an existing bathymetric survey to approximately 15 km offshore with complete coverage within the area of interest.
Uncertainty in the horizontal position of each sounding is a function of the total uncertainty propagated through each of the following component instruments: 1) vessel GPS, 2) intertial motion unit (IMU), 3) water sound velocity model, and 4) 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 1.5-degree sonar beam of the SeaBat 7111 results in horizontal uncertainty ranging from 0.15 m at 10 m slant range, to about 0.70 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 2 m x 2 m and 4 m x 4 m cell (each containing an average of 5 soundings for each 2 m cell, and 12 soundings for each 4 m cell) in CARIS. The mean standard deviation for all cells in the Estero Bay survey is 0.12 m, and 95 percent of the cells in the data set have a standard deviation of less than 0.30 m.
Sonar Data Collection
Bathymetric surveys were completed using a RESON SeaBat 7111 multibeam echosounder. The sonar was pole-mounted on the 34-foot USGS mapping vessel R/V Parke Snavely. GNSS position and inertial motion and orientation measurement data were recorded using an Applanix Position and Orientation Solutions for Marine Vessels (POS MV) 320 inertial-aided position and orientation system. The sonar head, GNSS antennae, and the inertial motion unit (IMU) were surveyed in place to a common reference frame with a Geodimeter 640 Total Station. The R/V Parke Snavely was outfitted with three networked workstations and a navigation computer for use by the captain and survey crew for data collection and initial processing.
Process_Date: 20120730
Geodetic Control
Geodetic control for the survey was established using the IN-Fusion SmartBase feature in the Applanix Position and Orientation System Post-Processing Package Mobile Mapping Suite (POSPac MMS, Version 6.1.4553.15282). IN-Fusion SmartBase is a feature in POSPac MMS that provides inertially-aided, carrier phase differential GNSS for mobile mapping platforms without requiring dedicated base receivers (Applanix, 2012). Instead, the software automatically selects a network of permanent GNSS reference stations accessible through the Internet and provides reference receiver coverage over the entire project area. The network of reference stations selected by the software changed slightly each day depending on the exact location of the survey vessel and the quality of the reference station data for the selected day.
Process_Date: 20120809
Vessel Position and Attitude
The R/V Parke Snavely was equipped with a POS MV 320 system, which records inertial-motion and GNSS position data for the duration of the survey. The POS MV provides real-time pitch information to the multibeam sonar system to facilitate pitch-compensation (see discussion below). As discussed in the Geodetic Control Section, the GNSS data are combined with the inertial-motion measurements within the POSPac MMS software and high-precision position and attitude corrections are exported as SBET files for merging with the multibeam data.
Process_Date: 20120809
Sound Velocity Measurements
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 provided time-of-flight sound-velocity measurements by using invar rods with a sound-velocity accuracy of +/- 0.06 m/s, pressure was measured by a semiconductor bridge strain gauge to an accuracy of 0.15 percent (500 dbar, full scale), and temperature was measured by thermistor with an accuracy of 0.05 degrees Celsius.
Process_Date: 20120809
Sonar Sounding Processing
CARIS HIPS and SIPS (version 7.1.0) bathymetry processing software was used to georeference the raw sonar data. The real-time attitude and position data was replaced with processed SBET data (described above); sound velocity corrections were applied; and the Total Propagated Uncertainty (TPU) for each sounding was estimated using Caris tools.
Process_Date: 20120809
Backscatter Image Production
Acoustic backscatter data were processed using Fledermaus (QPS) FMGeocoder software package (version 7.3.2). Survey line bathymetry data were exported from the Caris HIPS and SIPS (version 7.1) acquisition software as GSF files. These line files were paired with the original backscatter lines files (s7K) and imported into the FMGeocoder software. Each line file was radiometrically corrected and adjusted for Angle Varying Gain (AVG) with the “Flat” option with a window size of 30. All processed line files were merged together into one overall 2-m resolution backscatter mosaic. The processed backscatter dB values for a number of lines were adjusted using the backscatter adjustment tool to better match surrounding backscatter dB values. This tool allows the user to manually adjust dB values over entire lines. Often, the dB values within a line changed abruptly causing the mosaic to look “patchy.” Due to this manual adjustment process and abrupt changes in dB values, the backscatter mosaic may be more useful for visual interpretations rather than empirical characterizations that compare pixel values over the entire mosaic. Once finalized, the backscatter mosaic was exported as a geoTIFF, imported in ESRI ArcGIS and converted to a grid.
Process_Date: 20130218

Direct_Spatial_Reference_Method: raster
Raster_Object_Type: grid cell
Row_Count: 16020
Column_Count: 11456

Grid_Coordinate_System_Name: Universal Transverse Mercator
UTM_Zone_Number: 10
Scale_Factor_at_Central_Meridian: 0.9996
Longitude_of_Central_Meridian: -123
Latitude_of_Projection_Origin: 0.0
False_Easting: 500000
False_Northing: 0.0
Planar_Coordinate_Encoding_Method: row and column
Abscissa_Resolution: 2.0
Ordinate_Resolution: 2.0
Planar_Distance_Units: meters
Horizontal_Datum_Name: World Geodetic System 1984 (G1150)
Ellipsoid_Name: WGS 84
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257
Altitude_Datum_Name: World Geodetic System 1984 (G1150)
Altitude_Resolution: 0.01
Altitude_Distance_Units: meters
Altitude_Encoding_Method: Attribute values

Entity_Type_Label: Acoustic Bacscatter Amplitude
Acoustic backscatter shows the relative strength of the acoustic signal returned from the seafloor.
Entity_Type_Definition_Source: USGS

U.S. Geological Survey, Pacific Coastal and Marine Science Center (PCMSC)
Contact_Person: Steve Hartwell
Address_Type: mailing and physical address
Address: U.S. Geological Survey
Address: 400 Natural Bridges Drive
City: Santa Cruz
State_or_Province: CA
Postal_Code: 95060-5792
Country: US
Contact_Voice_Telephone: (831) 460-7814
Contact_Facsimile_Telephone: (831) 427-4748
Resource_Description: Downloadable Data
This information is not intended for navigational purposes.
This database has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
Format_Name: ESRI ASCII Grid
Format_Version_Number: 1.0
The ASCII file consists of header information containing a set of keywords, followed by cell values in row-major order. The file format is:

<NCOLS xxx>
<NROWS xxx>
row 1
row 2
row n

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 be 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.
Transfer_Size: 685 MB
Network_Resource_Name: <>
Fees: No cost

Metadata_Date: 20130129
Pacific Coastal and Marine Science Center (PCMSC), US Geological Survey
Address_Type: mailing address
Address: U.S. Geological Survey
Address: 400 Natural Bridges Drive
City: Santa Cruz
State_or_Province: California
Postal_Code: 95060
Country: USA
Contact_Voice_Telephone: (831) 460-7814
Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998

Generated by mp version 2.9.6 on Wed Nov 20 12:12:52 2013