Digital elevation model (DEM) of south San Francisco Bay, California, created using bathymetry data collected between 2005 and 2020 (MLLW)

Metadata also available as - [Outline] - [Parseable text] - [XML]

Frequently anticipated questions:

What does this data set describe?

Title:
Digital elevation model (DEM) of south San Francisco Bay, California, created using bathymetry data collected between 2005 and 2020 (MLLW)
Abstract:
A 1-m resolution, continuous surface, bathymetric digital elevation model (DEM) of the southern portion of San Francisco Bay, was constructed from bathymetric surveys collected from 2005 to 2020. In 2014 and 2015 the California Ocean Protection Council (OPC) contracted the collection of bathymetric surveys of large portions of San Francisco Bay. A total of 93 surveys were collected using a combination of multibeam and interferometric side-scan sonar systems. Of those 93 surveys, 75 consist of swaths of data ranging from 18- to just over 100-meters wide. These swaths were separated by data gaps ranging from 10- to just over 300-meters wide. The no-data areas required interpolation to create a continuous surface. The OPC surveys were combined with additional datasets collected by the United States Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA), NOAA National Ocean Service (NOS), and the United States Army Corps of Engineers (USACE) to create a continuous, high-resolution digital elevation model (DEM). The creation of this DEM refines techniques developed by the USGS to create DEMs from historic bathymetric data, and allow for the creation of a modern-day bathymetric surface that can be compared to earlier surveys to delineate regions of sediment erosion and deposition.
Supplemental_Information:
Additional information about the USGS field activities from which some of these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=b105SF https://cmgds.marine.usgs.gov/fan_info.php?fan=S0111SF https://cmgds.marine.usgs.gov/fan_info.php?fan=2016-678-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2019-614-FA
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., Jaffe, Bruce E., and Foxgrover, Amy C., 20210708, Digital elevation model (DEM) of south San Francisco Bay, California, created using bathymetry data collected between 2005 and 2020 (MLLW): data release DOI:10.5066/P9TJTS8M, 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., 2020, High-resolution (1 m) digital elevation model (DEM) of San Francisco Bay, California, created using bathymetry data collected between 1999 and 2020: data release DOI:10.5066/P9TJTS8M, 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: -122.392772
    East_Bounding_Coordinate: -121.970645
    North_Bounding_Coordinate: 37.762968
    South_Bounding_Coordinate: 37.416934
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/607df116d34e8564d67e3ae6?name=SouthSFBay_DEM_Mosaic_MLLW_1m.jpg&allowOpen=true (JPEG)
    Bathymetric map of the southern portion of San Francisco Bay (MLLW).
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2005
    Ending_Date: 2020
    Currentness_Reference:
    publication date of source DEMs
  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 38073 x 36939 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 1.0
      Ordinates (y-coordinates) are specified to the nearest 1.0
      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: Mean Lower Low Water (MLLW)
      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?
    floating point
    GeoTiff with elevation data associated with the digital elevation model (DEM) relative to MLLW. Cells with values of -3.4028231e+38 indicate no data. (Source: Producer defined)
    Value
    Elevation relative to MLLW (Source: Producer defined)
    Range of values
    Minimum:-29.16707611084
    Maximum:2.938999414444
    Units:meters
    Resolution:0.01
    Entity_and_Attribute_Overview:
    DEM in meters using MLLW datum showing bathymetric elevations of the southern portion of 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
    • Bruce E. Jaffe
    • Amy C. Foxgrover
  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 were compiled using new techniques to create a high-resolution DEM of the southern portion of San Francisco Bay, which will be used to document and assess changes in seafloor morphology. 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 elevations. 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?
    Source DEMS (source 1 of 1)
    Fregoso, Theresa A., 2021, Footprints and producers of source data used to create the southern portion of the high-resolution (1 m) San Francisco Bay, California, digital elevation model (DEM): U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution:
    Footprints of bathymetric source DEMS used to create high-resolution San Francisco Bay bathymetric surface.
  2. How were the data generated, processed, and modified?
    Date: 14-Dec-2020 (process 1 of 1)
    Using ArcGIS, the source DEMs were displayed and areas that would need further interpolation were identified. The lineage, vertical datum, and resolution of each DEM surface were noted for order of precedence when constructing the combined DEM and need for resampling or datum conversions. Using the ArcGIS Mosaic to New Raster tool, the surveys that were from the same sources, and were not continuous surfaces, were assembled into separate DEMs. Elevation contours were digitized across the DEMs to constrain the interpolation across data gaps in intervals of 20 centimeters across broader shallower areas (generally in water depths less than 4 m), and in intervals of 1 meter in deeper areas. The sections were converted from raster to points to use as inputs in the interpolation process. Using the ArcGIS Topo to Raster tool (ESRI 2015), the point data were used, along with the newly drawn contours, to interpolate continuous DEMs at a resolution of 1 meter, using the contours as the primary interpolation constraint. There were areas of multibeam data with varying resolutions, and in a different vertical datum from the rest of the data used in this project. The data were resampled to 1 meter using the resample tool in ArcGIS, and then converted to NAVD88 using NOAA’s VDATUM tool (https://vdatum.noaa.gov/). There were a few areas with data gaps that were filled using the Topo to Raster method from above. Once all data were in the same horizontal (UTM NAD83) and vertical (NAVD88) datums, the different DEMs were fitted together into a seamless DEM using the ArcGIS Mosaic to new Raster tool. In areas with obvious discrepancies between DEMs, edges were smoothed by clipping out a narrow gap between surveys using the pixel editor tool (ESRI 2020) to set the areas to no data, then filling in elevation holes. The final pieces were all put together using the Mosaic to new Raster tool, and VDATUM was again used to create versions in both Mean Lower Low Water (MLLW) and NAVD88. In 2004 NOAA created a specific NAVD88 to MLLW zones for the area of the 2005 USGS South Bay Survey. These zones have yet to be fully incorporated in the VDATUM grids. The NOAA change zones were used for the MLLW conversion in the regions of the 2005 USGS Survey. Vdatum was used for parts no included in the NOAA grid. The VDATUM tool did not have the full extents of the MLLW version available for conversion, so the pixel editor tool was used to interpolate based on the edges of the available data. Data sources used in this process:
    • Source DEMS
  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), 2020, Pixel Editor in ArcGIS Pro.

    Online Links:

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

    Online Links:

    United States Geological Survey (USGS), 2007, 2005 Hydrographic Survey of South San Francisco Bay, California.

    Online Links:

    • 2005 Hydrographic Survey of South San Francisco Bay, California

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. No further tests were conducted, and no claims are made to positional accuracy.
  3. How accurate are the heights or depths?
    Data are as accurate as source data used. No further tests were conducted, and no claims are made to vertical accuracy.
  4. Where are the gaps in the data? What is missing?
    Data set 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 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: None.
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 (SouthSFBay_DEM_Mosaic_MLLW_1m.tif) with accompanying files 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 ArcGIS software.

Who wrote the metadata?

Dates:
Last modified: 08-Jul-2021
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_P9TJTS8M/SouthSFBay_DEM_Mosaic_MLLW_1m_metadata.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:17:34 2021