Bathymetric change of Central San Francisco Bay, California: 1971 to 2020

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Frequently anticipated questions:

What does this data set describe?

Title:
Bathymetric change of Central San Francisco Bay, California: 1971 to 2020
Abstract:
This 25-m-resolution surface presents bathymetric change of Central San Francisco Bay, California (hereafter referred to as Central Bay). This surface compares a 1-m-resolution digital elevation model (DEM) of the central portion of San Francisco Bay (Fregoso and others, 2020), comprised of bathymetry data in the Central Bay region from the time period referred to as the 2010s because the majority of the surveys were in that decade, to a 25-m-resolution DEM of Central Bay comprised of historic surveys from 1971 to 1984 (referred to as the 1980s because the majority of the surveys were in that decade). Prior to creating this change surface, the 1-m-resolution 2010s DEM was resampled to match the 25-m-resolution 1980s Central Bay DEM, and the 1980s DEM corrected for grid interpolation bias and vertically referenced to the same tidal epoch as the 2010s DEM. The adjusted DEMs were then differenced to reveal amounts of sediment deposition and erosion that occurred between the surveys.
Supplemental_Information:
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 Esri format, this metadata file may include some Esri-specific terminology.
  1. How might this data set be cited?
    Fregoso, Theresa A., Foxgrover, Amy C., and Jaffe, Bruce E., 20240709, Bathymetric change of Central San Francisco Bay, California: 1971 to 2020: data release DOI:10.5066/P1332UUW, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    This is part of the following larger work.

    Fregoso, Theresa A., Jaffe, Bruce E., and Foxgrover, Amy C., 2024, Bathymetric change analysis in San Francisco Bay, California, from 1971 to 2020: data release DOI:10.5066/P1332UUW, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.516883
    East_Bounding_Coordinate: -122.196019
    North_Bounding_Coordinate: 37.989176
    South_Bounding_Coordinate: 37.722243
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/665a1b5bd34ef3137d36a70c?name=CentralBay_Bathychange_1971_2020.jpg&allowOpen=true (JPEG)
    Map showing bathymetric change of Central Bay, from 1971 to 2020, in meters.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1971
    Ending_Date: 2020
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Raster Digital Data Set
  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 1177 x 1121 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: -123.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 25.0
      Ordinates (y-coordinates) are specified to the nearest 25.0
      Planar coordinates are specified in Meter
      The horizontal datum used is D_NAD_1983_2011.
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: N/A, change is relative to adjusted 1980s DEM
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    floating point
    GeoTiff of bathymetric change between 1980s to 2010s digital elevation models (DEMs), Z-value in meters. Cells with values of -3.4028231e+38 indicate no data. (Source: Producer defined)
    Value
    Bathymetric change from 1980s to 2010s. Negative values indicate sediment erosion and positive values indicate sediment deposition. (Source: Producer defined)
    Range of values
    Minimum:-16.603319168091
    Maximum:23.271118164062
    Units:meters
    Resolution:0.01
    Entity_and_Attribute_Overview:
    Bathymetric change in meters from the 1980s to the 2010s in Central San Francisco Bay, California.
    Entity_and_Attribute_Detail_Citation:
    The entity and attribute information were generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Theresa A. Fregoso
    • Amy C. Foxgrover
    • Bruce E. Jaffe
  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?

These data are part of a sediment change analysis project of San Francisco Bay to understand current patterns of sediment gains and loss in efforts to help develop a sediment budget. These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems (GIS) or other software to identify changes in elevations between the two time periods. These data are not intended to be used for navigational purposes.

How was the data set created?

  1. From what previous works were the data drawn?
    2010s DEMS (source 1 of 12)
    Fregoso, Theresa A., Jaffe, Bruce E., and Foxgrover, Amy C., 2021, Digital elevation model (DEM) of Central San Francisco Bay, California, created using bathymetry data collected between 2009 and 2020 (MLLW): U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: 2010s DEM of Central Bay (MLLW) used for comparison
    H09185 (source 2 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1976, H09185: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09793 (source 3 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1981, H09793: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09794 (source 4 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1981, H09794: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09810 (source 5 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1982, H09810: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09811 (source 6 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1981, H09811: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09819 (source 7 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1983, H09819: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09844 (source 8 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1985, H09844: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09869 (source 9 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1984, H09869: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09873 (source 10 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1982, H09873: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H09927 (source 11 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1983, H09927: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
    H10080 (source 12 of 12)
    National Oceanic and Atmospheric Administration (NOAA), 1984, H10080: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution: data for 1980s bathymetric DEM for comparison
  2. How were the data generated, processed, and modified?
    Date: 2022 (process 1 of 6)
    Using ESRI’s Aggregate tool (Environmental Systems Research Institute, Inc., 2021), the 2010s DEM was converted to 25-m resolution. Data sources used in this process:
    • 2010s DEM
    Data sources produced in this process:
    • 2010s 25-m DEM
    Date: 2022 (process 2 of 6)
    1980s Central Bay bathymetric DEM was constructed using steps from Fregoso and others (2008) Data sources used in this process:
    • H09185
    • H09793
    • H09794
    • H09810
    • H09811
    • H09819
    • H09844
    • H09869
    • H09873
    • H09927
    • H10080
    Data sources produced in this process:
    • 1980s DEM
    Date: 2022 (process 3 of 6)
    The 1980s DEM was adjusted for changes in tidal epoch and grid bias by subtracting 7 cm for tidal change and subtracting 5.4 cm for bias adjustment. The resulting grid was snapped to the 2010s 25-m DEM. Data sources used in this process:
    • 1980s DEM
    • 2010s 25-m DEM
    Data sources produced in this process:
    • 1980s ADJ DEM
    Date: 2022 (process 4 of 6)
    The 1980s adjusted DEM was subtracted from the 25-m 2010s DEM to determine bathymetric changes in the intervening decades. Data sources used in this process:
    • 1980s ADJ DEM
    • 2010s 25-m DEM
    Data sources produced in this process:
    • 1980s-2010s Chg
    Date: 22-May-2024 (process 5 of 6)
    Edits were made to the GeoTIFF to correct the grid bias adjustment. A grid bias correction of 5.4 cm was added to the originally posted Central Bay 1971-2020 bathymetric change geoTIFF (CentralBay_Bathychange_1971_2020_25m.tif) to account for this correction being accidentally omitted from the 1980s DEM used to create the original difference DEM. As a result, the original geoTIFF mistakenly underestimated deposition (positive values) and overestimated erosion (negative values) by a static offset of 5.4 cm. Within the metadata, the Attribute Range Domain minimum and maximum values were corrected to reflect this 5.4 cm shift and the last two sentences of the abstract edited to clarify that the 1980s DEM was corrected for both grid interpolation bias and a tidal datum adjustment prior to calculating the change DEM. The metadata available from a harvester may supersede metadata bundled within a download file. Users are advised to compare the metadata date of this file to any similar file to ensure they are using the most recent version. (afoxgrover@usgs.gov) Data sources used in this process:
    • 1980s-2010s Chg
    Data sources produced in this process:
    • 1980s-2010s Chg2
    Date: 22-May-2024 (process 6 of 6)
    Edits were made to the GeoTIFF’s internal projection assignment and to the altitude datum listed in the metadata. Although the horizontal datum and projection information were correctly defined as NAD83(2011) / UTM Zone 10 within the metadata files, the Geographic Coordinate System (GCS) and associated DATUM definition description stored internally, within the GeoTIFF itself, was incorrect. The originally assigned GCS was corrected from GCS_GRS_1980 to NAD 1983 (2011) and the projected coordinate system (PCS) from GRS_1980_UTM_Zone_10N to NAD 1983 (2011) UTM Zone 10N. Please note that the coordinate values and position of the GeoTIFF pixels did not change, only the projection definition. Within the metadata, the Altitude Datum Name, previously listed as Mean Lower Low Water (MLLW), was corrected. Although the input bathymetric DEMs are both referenced to MLLW, the change grid represents relative change between the two time periods and is not directly referenced to MLLW. This clarification was also applied to the Entity Type and Attribute Definition fields. The metadata available from a harvester may supersede metadata bundled within a download file. Users are advised to compare the metadata date of this file to any similar file to ensure they are using the most recent version. (afoxgrover@usgs.gov) Data sources used in this process:
    • 1980s-2010s Chg2
    Data sources produced in this process:
    • 1980s-2010s Prj
  3. What similar or related data should the user be aware of?
    International Hydrographic Organization (IHO), 2008, IHO standards for hydrographic surveys (5th ed.).

    Online Links:

    Environmental Systems Research Institute, Inc (ESRI), 2015, Topo to Raster help page.

    Online Links:

    Environmental Systems Research Institute, Inc (ESRI), 2021, Aggregate (Spatial Analyst).

    Online Links:

    National Oceanic and Atmospheric Administration (NOAA), 2019, Vertical Datum Transformation (VDatum).

    Online Links:

    Fregoso, Theresa A., Foxgrover, Amy C., and Jaffe, Bruce E., 2008, Sediment deposition, erosion, and bathymetric change in central San Francisco Bay: 1855-1979.

    Online Links:

    • https ://doi.org/10.3133/ofr20081312

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?
    Data are as accurate as source data used. Users are advised to read the metadata record for the sources for horizontal accuracy details. No further accuracy tests were conducted.
  3. How accurate are the heights or depths?
    Data are as accurate as source data used. Users are advised to read the metadata record for the sources for vertical accuracy details. No further accuracy tests were conducted.
  4. Where are the gaps in the data? What is missing?
    Data are 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 consistency tests were conducted.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints
Use_Constraints 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(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    US

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available as a GeoTiff (CentralBay_BathyChange_1971_2020.tif) with an accompanying world file (.tfw) and FGDC-compliant metadata.
  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?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with GIS software.

Who wrote the metadata?

Dates:
Last modified: 09-Jul-2024
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)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P1332UUW/CentralBay_BathyChange_1971_2020_metadata.faq.html>
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