Eelgrass distributions derived from a towed underwater video survey of the Nisqually River delta, 2017

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Frequently anticipated questions:

What does this data set describe?

Title:
Eelgrass distributions derived from a towed underwater video survey of the Nisqually River delta, 2017
Abstract:
This portion of the USGS data release presents eelgrass distributions derived from towed underwater video surveys of the Nisqually River delta, Washington in 2017 (USGS Field Activity Number 2017-614-FA). Eelgrass data were collected from the R/V George Davidson equipped with a towed underwater video system and global navigation satellite system (GNSS) receiver. The underwater video system consisted of a Splashcam standard definition video camera connected to a Sony GV-D1000 video monitor and tape recorder. Positioning of the survey vessel was determined at 1 Hz intervals using a Trimble R7 GNSS receiver and Trimble Zephyr Model 2 antenna. The positioning data from the GNSS were encoded onto the audio track of the digital video recording using Red Hen Systems (RHS) VMS200 hardware. Underwater video data were recorded as the vessel navigated along a series of shore-perpendicular transects at speeds between 1 and 2 knots. The underwater video recording was later reviewed and the presence or absence of eelgrass was determined for each 1-s segment of video tape. These data were used to evaluate the classification of single-beam sonar data acquired during the same time period.
Supplemental_Information:
Additional information about the field activities from which these data were derived are available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=2017-614-FA
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Stevens, Andrew W., Takesue, Renee K., and Grossman, Eric E., 20200721, Eelgrass distributions derived from a towed underwater video survey of the Nisqually River delta, 2017: data release DOI:10.5066/P9N9K2I1, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Stevens, Andrew W., Takesue, Renee K., and Grossman, Eric E., 2020, Eelgrass distributions and bathymetry of the Nisqually River delta, Washington: data release DOI:10.5066/P9N9K2I1, 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: -122.7460220
    East_Bounding_Coordinate: -122.6841300
    North_Bounding_Coordinate: 47.1185910
    South_Bounding_Coordinate: 47.1044550
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 23-Feb-2017
    Ending_Date: 23-Feb-2017
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text
  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):
      • Point (4470)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 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.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 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 dataset (Source: Producer defined)
    datetime_utc
    The date and time of data collection in Coordinated Universal Time (UTC). (Source: Producer Defined)
    Range of values
    Minimum:2017-02-23 17:14:45
    Maximum:2017-02-23 19:36:17
    Units:date and time in yyyy-mmm-dd HH:MM:SS format
    longitude
    Longitude coordinate of data point relative to the North American Datum of 1983 (Source: Producer defined)
    Range of values
    Minimum:-122.7460220
    Maximum:-122.6841300
    Units:Decimal degrees
    latitude
    Latitude coordinate of data point relative to the North American Datum of 1983 (Source: Producer defined)
    Range of values
    Minimum:47.1044550
    Maximum:47.1185910
    Units:Decimal degrees
    easting_m
    East coordinate of data point relative to the North American Datum of 1983, projected in the Universal Transverse Mercator (UTM) Zone 10 North, meters, coordinate system (Source: Producer defined)
    Range of values
    Minimum:519267.23
    Maximum:523965.80
    Units:meters
    northing_m
    North coordinate of data point relative to the North American Datum of 1983,projected in the Universal Transverse Mercator (UTM) Zone 10 North, meters, coordinate system (Source: Producer defined)
    Range of values
    Minimum:5216808.50
    Maximum:5218374.68
    Units:meters
    tape_id
    Numeric identifier for the physical digital-8 tape used to record the underwater video data (Source: Producer defined)
    Range of values
    Minimum:1
    Maximum:2
    Units:meters
    veg_flag
    Flag that indicates the presence or absence of eelgrass at each location along the survey track (Source: producer defined)
    ValueDefinition
    0eelgrass absent
    1eelgrass present

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Andrew W. Stevens
    • Renee K. Takesue
    • Eric E. Grossman
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    PCMSC Science Data Coordinator
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

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

Why was the data set created?

Data were obtained to document interannual changes in eelgrass distributions following the removal of a dike that restored tidal processes to over 300 ha of former freshwater wetlands on the Nisqually River delta in 2009. 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 distributions of eelgrass.

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: 23-Feb-2017 (process 1 of 3)
    Eelgrass distribution data were collected from the R/V George Davidson equipped with a towed underwater video system and global navigation satellite system (GNSS) receiver. The underwater video system consisted of a Splashcam standard definition video camera connected to a Sony GV-D1000 video monitor and tape recorder. Positioning of the survey vessel was determined at 1-Hz intervals using a Trimble R7 GNSS receiver and Trimble Zephyr Model 2 antenna. The positioning data from the GNSS were encoded onto the audio track of the digital video recording using Red Hen Systems (RHS) VMS200 hardware. Underwater video data were recorded as the vessel navigated along a series of shore-perpendicular transects at speeds between 1 and 2 knots.
    Date: 23-Apr-2020 (process 2 of 3)
    The underwater video recording was reviewed and the presence or absence of eelgrass was determined for each 1-s segment of video tape. All available eelgrass distribution data from the survey were compiled into a comma-delimited text file for distribution.
    Date: 19-Oct-2020 (process 3 of 3)
    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?
    Gibbs, Ann, Grossman, Eric, and Richmond, Bruce, 2005, Summary and preliminary interpretations of USGS cruise A-2-02-HW: Underwater video surveys collected off of Oahu, Molokai, and Maui, Hawaii June-July 2002: U.S. Geological Survey, Reston, VA.

    Online Links:

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?
    Positioning of the survey vessel was achieved with a global navigation satellite system (GNSS) differentially corrected with data from a single GNSS base station. The average estimated horizontal accuracy of the GNSS-derived vessel positions is 5 cm. However, horizontal offsets between the underwater video camera and the shipboard GNSS antenna, or layback, was observed during data collection. The layback of the video camera is estimated to be no greater than 15 m based on calculations for a similar camera system given in Gibbs and others, 2005.
  3. How accurate are the heights or depths?
    No formal positional accuracy tests were conducted
  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?
    All data falls within expected ranges.

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
    U.S. Geological Survey
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    USA

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Eelgrass distribution data are available as a comma-delimited text file, along with associated 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?

Who wrote the metadata?

Dates:
Last modified: 19-Oct-2020
Metadata author:
PCMSC Science Data Coordinator
U.S. Geological Survey, Pacific Coastal and Marine Science Center
2885 Mission St.
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_P9N9K2I1/nq17_video_metadata.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:17:24 2021