Gridded bathymetric data from repeat 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, Gridded bathymetric data from repeat 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, Oceanographic and hydrographic monitoring data of a shallow-water placement of dredged sediment 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: -122.191551
   East_Bounding_Coordinate: -122.157713
   North_Bounding_Coordinate: 37.609115
   South_Bounding_Coordinate: 37.575494
   

3. What does it look like?

   dmp_bathy_grids.png (PNG)

   Elevations derived from each bathymetry 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?
      

      Indirect_Spatial_Reference:

      Single beam transect lines were oriented in the cross channel direction and spaced at 90 m intervals along channel centered on the dredged sediment placement area, and are comprised of 0.5 m continuous gridded surfaces. Swath survey lines went along the placement area; the distance between lines may have varied due to swath coverage dependence on water depth.

      This is a Raster data set. It contains the following raster data types:
      • Dimensions 7513 x 5853 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 0.5
      Ordinates (y-coordinates) are specified to the nearest 0.5
      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.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: North America Vertical Datum 1988
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:

      Explicit elevation coordinate included with horizontal coordinates

7. How does the data set describe geographic features?

   Attribute Table

   Table containing attribute information associated with the data set (Source: Producer defined)

   Elevation

   Elevation in meters relative to the NAVD88 vertical datum. No data value is -9999. (Source: Producer Defined)

   Range of values
   Minimum:	-3.53648
   Maximum:	0.109048
   Units:	meters

   Entity_and_Attribute_Overview:

   Single-beam bathymetric data from south San Francisco Bay that are gridded into 50-cm base surfaces in the UTM Zone 10 North, NAD83(2011) coordinate system.

   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 3)

   All six bathymetric surveys performed with the SwathPlus sonar system 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 survey vessel. During the mapping mission, an Applanix POS-MV (Position and Orientation System for Marine Vessels) was used to position the vessel, 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. Soundings were cleaned for obvious errors and gridded into a 50-cm base surfaces. The base surfaces were exported as Erdas Imagine files in UTM Zone 10 North, WGS84 coordinates vertically referenced to the WGS84 ellipsoid. The data were transformed from WGS84 to NAD83 horizontal coordinates using ArcGIS Pro ArcTool raster projection command WGS_1984_(ITRF08)_To_NAD_1983_2011. NOAA's on-line VDATUM transformation tool states there is a +33.062 difference between WGS84 and NAVD88 elevations (vertical uncertainty of 0.06 m) at a point in the center of the survey area. A value of 33.062 was added to the original bathymetric grids to transform from WGS-84 elevations to NAVD88 elevations. The NAVD88 bathymetric grids were then exported as a GeoTIFF files in UTM zone 10, NAD83(2011) coordinates.

   Date: 2025 (process 2 of 3)

   Bathymetric surveys performed with single beam sonar systems were conducted using the same mapping systems and post-processed using the same methodology. The data were collected from personal watercraft equipped with a CEEHydrosystems Ceescope single beam sonar system with a 200 kHz and 9-degree beam angle. Initially, the survey design included a total of 40 survey lines that were oriented in the cross channel direction and spaced at 90 m intervals along channel centered on the dredged sediment placement area. The survey design was adjusted for the final single-beam survey to better characterize the sediment deposits that formed as a result of the dredged sediment placements. The updated survey design included a total of 111 cross channel transects spaced at about 23 m intervals and reduced the spatial extent of the survey area. Positions of the survey platforms were recorded at 10 Hz intervals during the mapping missions with a Trimble BD990 GNSS receiver. Sound-velocity profiles were collected throughout the survey days with a Castaway CTD. Positioning data from the GNSS receivers were post-processed using Waypoint Grafnav software to apply differential corrections from the National Geodetic Survey (NGS) Continuously Operating Reference Station Site, P222, located approximately 10 km away with horizontal and vertical coordinates relative to the North American Datum of 1983 (2011 realization). Orthometric elevations relative to the NAVD88 vertical datum were computed using NGS Geoid18 offsets. Bathymetric data were merged with post-processed positioning data and spurious soundings were removed using a custom Graphical User Interface (GUI) programmed with the computer program MATLAB. The processed data were projected using the UTM Zone 10 North meters coordinate system and continuous gridded surfaces with a horizontal resolution of 0.5 m were produced using linear interpolation.

   Date: 2025 (process 3 of 3)

   Initial inspection of the bathymetric surfaces revealed differences in elevations between the SwathPlus and single-beam surveys in regions where bathymetric change was not expected to be observed. Static vertical adjustments were therefore applied to each bathymetric surface to eliminate the mean bias based on comparisons between the initial swath survey and subsequent surveys in relatively flat areas where bathymetric change was assumed to be negligible. The mean static vertical corrections applied to the successive SwathPlus and single beam survey data were -2 cm and -13 cm, respectively.

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?
   The SWATHPlus sonar system (234 kHz) depth accuracy reduces with horizontal range. The system has an estimated vertical depth uncertainty ranging from about 0.05 m to 0.34 m over a horizontal range of 0 to 90 m (www.iter-systems.com/wp-content/uploads/2020/01/IHO-standards-data-quality.pdf). The CEE Hydrosystems Ceescope single beam echosounders have a vertical accuracy of 1 cm + 1 percent of water depth (https://ceehydrosystems.com/products/single-beam-echo-sounders/ceescope/). 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.
2. How accurate are the geographic locations?
   The SwathPlus sonar system utilized an Applanix POS-MV was used for positioning. 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). The Ceescope sonar systems used a Trimble BD990 dual frequency global satellite navigation system receiver for positioning during the single beam sonar surveys. Manufacturer reported accuracy in the post-processed horizontal positions from the Trimble BD990 GNSS rover trajectories is 0.8 cm + 1 ppm (https://oemgnss.trimble.com/en/products/receiver-modules/bd990), resulting in an average horizontal accuracy of 1.8 cm given an average baseline length of 10 km. 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?
   The post-processed vertical positional accuracy from the Applanix POS-MV used in the SwathPlus bathymetric surveys is about 0.2 m (https://www.applanix.com/downloads/products/specs/posmv/POS-MV-WaveMaster-II.pdf). Manufacturer reported accuracy in the post-processed vertical positions from the Trimble BD990 GNSS rover trajectories is 1.5 cm + 1 ppm (https://oemgnss.trimble.com/en/products/receiver-modules/bd990), resulting in an average horizontal accuracy of 2.5 cm given an average baseline length of 10 km. 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.
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 (.tif) 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_st_c.tif, where "yyyy" denotes the survey year, "mm" denotes the survey month, "dd" is the final day of data collection, and "st" provides the type of survey and is either "sw" for SwathPlus or "sb" for single beam.
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 GeoTIFF (.tif) version of the bathymetry data. in format GeoTIFF (version ArcMap (version 10.3.1)) Size: 51.3
     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 files have 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)