Acoustic-backscatter data from repeat side-scan sonar surveys of south San Francisco Bay, California, 2023-2025

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Dartnell, Peter, Stevens, Andrew W., and Lacy, Jessica R., 20250820, Acoustic-backscatter data from repeat side-scan sonar surveys of south San Francisco Bay, California, 2023-2025: data release DOI:10.5066/P14D723N, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

   Online Links:

   • https://doi.org/10.5066/P14D723N

   This is part of the following larger work.
   McGill, Samantha C., Lacy, Jessica R., Stevens, Andrew W., Allen, Rachel M., Dartnell, Peter, Thede, Joanne C., Tan, Angela C., and Hatcher, Gerald A., 2025, Hydrodynamic, bathymetric, and sediment transport data spanning dredge material placement in south San Francisco Bay, California, 2023-2025: data release doi:10.5066/P14D723N, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

   Online Links:

   • https://doi.org/10.5066/P14D723N

   Other_Citation_Details:

   Suggested Citation: McGill, S.C., Lacy, J.R., Stevens, A.W., Allen, R.M., Dartnell, P., Thede, J.C., Tan, A.C., and Hatcher, G.A., 2025, Hydrodynamic, bathymetric, and sediment transport data spanning dredge material placement in south San Francisco Bay, California, 2023-2025: U.S. Geological Survey data release, https://doi.org/10.5066/P14D723N.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -122.182946
   East_Bounding_Coordinate: -122.168298
   North_Bounding_Coordinate: 37.607479
   South_Bounding_Coordinate: 37.577268
   

3. What does it look like?

   DMP23_backscatter_intensity.png (PNG)

   Maps showing acoustic backscatter for each SwathPlus survey.

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 25-Oct-2023

   Ending_Date: 15-Jan-2025

   Currentness_Reference:

   ground condition at time data were collected.

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: GeoTIFF
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 3343 x 1266 x 1, type Grid Cell
   2. What coordinate system is used to represent geographic features?
      

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:

      UTM_Zone_Number: 10
      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.00000
      Latitude_of_Projection_Origin: 0.00000
      False_Easting: 500000.0
      False_Northing: 0.00
      

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 1.0
      Ordinates (y-coordinates) are specified to the nearest 1.0
      Planar coordinates are specified in Meters
      The horizontal datum used is North American Datum of 1983, 2011 realization (NAD83(2011)).
      The ellipsoid used is GRS80.
      The semi-major axis of the ellipsoid used is 6378137.00.
      The flattening of the ellipsoid used is 1/298.257222101.
      
7. How does the data set describe geographic features?

   Attribute Table

   backscatter intensity as a digital value (Source: Producer defined)

   Value

   Acoustic-backscatter value. No data value is -9999. (Source: Producer Defined)

   Range of values
   Minimum:	0
   Maximum:	274
   Units:	none

   Entity_and_Attribute_Overview:

   The complete 1-m resolution of south San Francisco Bay backscatter raster is an 8-bit integer raster. It has a minimum (least reflective) value of 0 and a maximum (most reflective) value of 274.

   Entity_and_Attribute_Detail_Citation: U.S. Geological Survey
   

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Peter Dartnell
   • Andrew W. Stevens
   • Jessica R. Lacy
2. Who also contributed to the data set?
3. To whom should users address questions about the data?
   U.S. Geological Survey, Pacific Coastal and Marine Science Center

   Attn: PCMSC Science Data Coordinator

   2885 Mission Street

   Santa Cruz, CA
   

   831-427-4747 (voice)

   pcmsc_data@usgs.gov

Why was the data set created?

How was the data set created?

1. From what previous works were the data drawn?
2. How were the data generated, processed, and modified?

   Date: 2025 (process 1 of 1)

   Surveys were conducted on October 25-26, 2023, January 8-9, 2024, January 23-25, 2024, March 6-8, 2024, October 15-16, 2024, January 14-15, 2025. All six surveys were conducted using the same mapping systems and post-processed using the same methodology. The data were collected with a SWATHplus-M 234-kHz interferometric side-scan sonar system pole-mounted on the U.S. Geological Survey (USGS) R/V Parke Snavely. During the mapping mission, an Applanix POS-MV (Position and Orientation System for Marine Vessels) was used to position the vessel during data collection, and it also accounted for vessel motion such as heave, pitch, and roll. The POS-MV also recorded position and vessel motion parameters for later post-processing. Sound-velocity profiles were collected throughout the survey days with a Castaway CTD. Post-processed POS-MV Smoothed Best Estimate of Trajectory (SBET) files were merged with the survey line files using BathySwath software and then the line files were imported into SonarWiz software. Acoustic-backscatter data were processed using SonarWiz software techniques and gridded into 1-m resolution images. The images were exported as Erdas Imagine files in UTM zone 10, WGS-84 coordinates and imported into a GIS (ArcGIS Pro). The images were then projected to UTM zone 10, NAD83(2011) coordinates using ArcTools raster projection tool. The images were exported as a GeoTIFF file in UTM zone 10, NAD83(2011) coordinates.

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?
   No formal attribute accuracy tests were conducted.
2. How accurate are the geographic locations?
   The Applanix POS-MV post-processed horizontal positional accuracy is about 0.1 m with roll and pitch accuracies of about 0.02 degrees (https://www.applanix.com/downloads/products/specs/posmv/POS-MV-WaveMaster-II.pdf). Accuracies of final products may be lower due to total propagated uncertainties of the mapping systems, which include sonar system, position and motion compensation system, and navigation, as well as data processing that includes sounding cleaning, gridding, and datum transformations.
3. How accurate are the heights or depths?
   Not applicable to acoustic-backscatter data.
4. Where are the gaps in the data? What is missing?
   Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
5. How consistent are the relationships among the observations, including topology?
   No formal logical accuracy tests were conducted.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey - CMGDS

   2885 Mission Street

   Santa Cruz, CA
   

   831-427-4747 (voice)

   pcmsc_data@usgs.gov
2. What's the catalog number I need to order this data set? These data are available in GeoTIFF format, accompanied by CSDGM FGDC-compliant metadata. The survey dates and type of sonar used in the surveys are denoted in the filenames according to the following convention: yyyy_mm_dd_bs.tif, where "yyyy" denotes the survey year, "mm" denotes the survey month, and "dd" is the final day of data collection.
3. What legal disclaimers am I supposed to read?
   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.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:	Downloadable zip file contains the TIFF (.tif) version of the acoustic-backscatter data and a projection file (.tfw). in format GeoTIFF (version Globalmapper (version 23.0)) Size: 5.4
     Network links:	https://doi.org/10.5066/P14D723N

   • Cost to order the data: None.

5. What hardware or software do I need in order to use the data set?
   The downloadable data file has been compressed with the "zip" command and can be unzipped with Winzip (or other tool) on Windows systems. To utilize these data, the user must have software capable of uncompressing the WinZip file and importing and viewing a GeoTIFF file.

Who wrote the metadata?

Dates:

Last modified: 20-Aug-2025

Metadata author:

U.S. Geological Survey, Pacific Coastal and Marine Science Center

Attn: PCMSC Science Data Coordinator

2885 Mission Street

Santa Cruz, CA

831-427-4747 (voice)

pcmsc_data@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)