Bathymetric measurements of Little Holland Tract, Sacramento-San Joaquin Delta, California, 2015, from personal watercraft

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Frequently anticipated questions:

What does this data set describe?

Title:
Bathymetric measurements of Little Holland Tract, Sacramento-San Joaquin Delta, California, 2015, from personal watercraft
Abstract:
Bathymetric data were collected by the U.S. Geological Survey (USGS) in 2015 for Little Holland Tract in the Sacramento-San Joaquin River Delta, California. The data were collected using a personal watercraft (PWC) platform that consisted of Trimble R7 Global Navigation Satellite System (GNSS) receivers with Zephyr 2 antennas, combined with Odom Echotrac CV-100 single-beam echosounders and 200 kHz transducers. Data was post-processed to remove spurious data points. Raw depths were converted to ellipsoid elevations in the data acquisition software. Orthometric elevations relative to NAVD88 were computed using National Geodetic Survey Geoid12a offsets, and the final data were projected in Cartesian coordinates using the UTM Zone 10 North (meters) (NAD83[2011]) coordinate system. The mean estimated vertical uncertainty of the 2015 USGS PWC survey is 6.1 cm.
Supplemental_Information:
Additional information about the field activities from which these data were derived are available online at: http://cmgds.marine.usgs.gov/fan_info.php?fan=2015-642-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?
    Snyder, Alexander G., Stevens, Andrew W., Carlson, Emily, and Lacy, Jessica R., 2016, Bathymetric measurements of Little Holland Tract, Sacramento-San Joaquin Delta, California, 2015, from personal watercraft: data release DOI:10.5066/F7RX9954, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Snyder, Alexander G., Stevens, Andrew W., Carlson, Emily, and Lacy, Jessica R., 2016, Digital elevation model of Little Holland Tract, Sacramento-San Joaquin Delta, California, 2015: data release DOI:10.5066/F7RX9954, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -121.667629767
    East_Bounding_Coordinate: -121.648939185
    North_Bounding_Coordinate: 38.350195381
    South_Bounding_Coordinate: 38.28554843
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 08-Jun-2015
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text and shapefile
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Entity point (652120)
    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 coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in Meter
      The horizontal datum used is D_North_American_1983.
      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.
  7. How does the data set describe geographic features?
    Attribute Table
    Table containing attribute information associated with the data set. (Source: Producer defined)
    Date_Time
    Date and time that data point was collected in local Pacific Standard Time, yyy-mm-dd hh:mm:ss.sss. (Source: Producer defined) Unknown
    Longitude
    Longitude coordinate of data point (NAD83 (2011)). (Source: Producer defined)
    Range of values
    Minimum:121.64894
    Maximum:121.667058
    Units:Decimal Degrees
    Latitude
    Latitude coordinate of data point (NAD83 (2011)). (Source: Producer defined)
    Range of values
    Minimum:38.285711
    Maximum:38.350002
    Units:Decimal Degrees
    Easting_m
    Easting projected coordinate of data point - NAD83(2011), UTM Zone 10. (Source: Producer defined)
    Range of values
    Minimum:616525.65
    Maximum:618056.1
    Units:Meters
    Northing_m
    Northing projected coordinate of data point - NAD83(2011), UTM Zone 10. (Source: Producer defined)
    Range of values
    Minimum:4238359.71
    Maximum:4245512.56
    Units:Meters
    Ellip_Ht_m
    Height of data point with reference to the ellipsoid. (Source: Producer defined)
    Range of values
    Minimum:-290.29
    Maximum:220.24
    Ortho_Ht_m
    Elevation with reference to Geoid 12A. (Source: Producer defined)
    Range of values
    Minimum:-9.8
    Maximum:1.03
    Units:Meters
    Hor_Acc_m
    The uncertainty associated with positioning of the survey platforms, estimated by computing the standard deviations of the GNSS rover positions relative to the base station using Waypoint Grafnav. (Source: Producer defined)
    Range of values
    Minimum:0.02
    Maximum:33.01
    Units:Meters
    Vert_Acc_m
    The uncertainty associated with positioning of the survey platforms, estimated by computing the standard deviations of the GNSS rover positions relative to the base station using Waypoint Grafnav. (Source: Producer defined)
    Range of values
    Minimum:0.03
    Maximum:41.37
    Units:Meters
    Entity_and_Attribute_Overview:
    The entity and attribute information provided here describes the tabular data associated with the data set. Please review the detailed descriptions that are provided (the individual attribute descriptions) for information on the values that appear as fields/table entries of the data set.
    Entity_and_Attribute_Detail_Citation:
    The entity and attribute information was 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)
    • Alexander G. Snyder
    • Andrew W. Stevens
    • Emily Carlson
    • 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
    US

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

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.

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: 08-Jun-2015 (process 1 of 6)
    Bathymetric data were collected primarily using two personal watercraft (PWC), equipped with single-beam echosounders and dual-frequency global navigation satellite systems (GNSS) receivers. The sonar systems consisted of Odom Echotrac CV-100 single-beam echosounders and 200 kHz transducers with 9-degree beam angles that digitize depth returns at a resolution of 1.25 cm. Positioning of the survey vessels was determined at 10-Hz using Trimble R7 GNSS receivers with Zephyr 2 antennas operating in autonomous mode. Output from the GNSS and sonar systems were combined in real time on the PWC by a computer running HYPACK (version 13.0.0.6) hydrographic survey software. Navigation and data quality information were displayed on a video monitor, allowing PWC operators to navigate along survey lines at speeds of 2 to 3 meters per second. Depths from the echosounders were computed using a sound velocity of 1488.80 meters per second, measured during the survey with a YSI Castaway CTD. Digitized depths were compared to the raw acoustic backscatter signal using a Graphical User Interface (GUI) programmed using the computer program Matlab to ensure the accuracy of depths produced by the echosounder. In areas where the automated echosounder signal processing failed (typical in very shallow regions), the GUI was used to digitize the bottom by hand. Once the raw depths were adjusted, a running mean with a window length of 5 points (approximately 1 m distance) was used to remove high-frequency vertical fluctuations, such as those caused by pitch and roll of the survey vessels.
    Date: 19-Jun-2015 (process 2 of 6)
    Data collection using same methods as above.
    Date: Jun-2015 (process 3 of 6)
    Survey-grade positioning of the PWCs were obtained using a post-processed kinematic (PPK) methodology, whereby Waypoint Grafnav (version 8.50) was used to make differential corrections referenced to a single base station described in the previous section. The post-processed positioning data were then merged with sonar depths to determine the elevation of the bed. Orthometric elevations relative to NAVD88 were computed using the National Geodetic Survey Geoid12a, and the final data were projected in Cartesian coordinates using the UTM Zone 10 North (meters) coordinate system.
    Date: 17-Nov-2015 (process 4 of 6)
    All data were compiled into a single shapefile.
    Date: Nov-2025 (process 5 of 6)
    Edits were made as needed to bring the metadata up to current PCMSC standards including standardizing doi# links, correcting typos, adding disclaimers, and refining keywords. Point of Contact and Metadata Contact information sections were changed to static PCMSC contact information. No data were changed. Users are advised to compare the metadata date of this file to any similar file to ensure they are using the most recent version. Person who carried out this activity:
    Susan A Cochran
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission St.
    Santa Cruz, CA
    United States

    831-460-7545 (voice)
    scochran@usgs.gov
    Date: 19-Oct-2020 (process 6 of 6)
    Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  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 uncertainty associated with positioning of the survey platforms was estimated by computing the standard deviations of the GNSS rover positions relative to the base station using Waypoint Grafnav (version 8.50). Depths measured using sonar are subject to additional sources of uncertainty including fluctuations in the speed of sound and from the pitch and roll of the survey vessels. Given the relatively calm water surface and low range of water depth present in this survey, we estimate depth sounding uncertainty to be 1 percent of the water depth.
  2. How accurate are the geographic locations?
    The uncertainty associated with positioning of the survey platforms was estimated by computing the standard deviations of the GNSS rover positions relative to the base station using Waypoint Grafnav (version 5.0). Based on these calculations, the mean horizontal accuracy of GNSS positions at the 95 percent confidence interval (1.96 times the standard deviations assuming a normal distribution) is 3.5 cm.
  3. How accurate are the heights or depths?
    The uncertainty associated with positioning of the survey platforms was estimated by computing the standard deviations of the GNSS rover positions relative to the base station using Waypoint Grafnav (version 5.0). Based on these calculations, the mean vertical accuracy of GNSS positions at the 95 percent confidence interval (1.96 times the standard deviations assuming a normal distribution) were calculated. Depths measured using sonar are subject to additional sources of uncertainty including fluctuations in the speed of sound and from the pitch and roll of the survey vessels. Given the relatively calm water surface and low range of water depth present in this survey, we estimate depth sounding uncertainty to be 1 percent of the water depth. The mean estimated vertical uncertainty is 6.1 cm.
  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?
    Data fall within expected ranges, efforts were made during digital elevation modeling to best represent reality.

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 navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - Science Base
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Bathymetry data are available as both a comma-delimited text file and a shapefile, and include the associated 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. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 19-Oct-2020
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA
US

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_F7RX9954/LHT15_PWCsonar_FGDC.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:17:20 2021