Nearshore bathymetry data from northern Monterey Bay, California, September and October 2015

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Frequently anticipated questions:


What does this data set describe?

Title:
Nearshore bathymetry data from northern Monterey Bay, California, September and October 2015
Abstract:
This part of the data release presents bathymetry data from northern Monterey Bay, California collected in September and October 2015 using two personal watercraft (PWCs). The PWCs were equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers.
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=2015-668-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., and Snyder, Alexander G., 2017, Nearshore bathymetry data from northern Monterey Bay, California, September and October 2015: data release DOI:10.5066/F76H4GCW, 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., Logan, Joshua B., Snyder, Alexander G., Hoover, Daniel J., Barnard, Patrick L., and Warrick, Jonathan A., 2017, Beach topography and nearshore bathymetry of northern Monterey Bay, California: data release DOI:10.5066/F76H4GCW, U.S. Geological Survey, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.041021
    East_Bounding_Coordinate: -121.789825
    North_Bounding_Coordinate: 36.978306
    South_Bounding_Coordinate: 36.805306
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 28-Sep-2015
    Ending_Date: 01-Oct-2015
    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 (1345069)
    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 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983, 2011 realization.
      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: 0.001
      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)
    Date and Time (yyyy-mm-dd HH:MM:SS.FFF)
    The date and time of data collection in Greenwich Mean Time (GMT). (Source: Producer Defined)
    Range of values
    Minimum:2015-09-28 15:45:01.514
    Maximum:2015-10-01 19:50:45.068
    Units:date and time in mm/dd/yyyy HH:MM:SS.FFF format
    Longitude (deg. E)
    Longitude coordinate of data point relative to the North American Datum of 1983 (2011 realization) (Source: Producer defined)
    Range of values
    Minimum:-122.041021
    Maximum:-121.789825
    Units:Decimal degrees
    Latitude (deg. N)
    Latitude coordinate of data point relative to the North American Datum of 1983 (2011 realization) (Source: Producer defined)
    Range of values
    Minimum:36.805306
    Maximum:36.978306
    Units:Decimal degrees
    Easting (m)
    East coordinate of data point relative to the North American Datum of 1983 (2011 realization), projected in the Universal Transverse Mercator (UTM), Zone 10 North, meters, coordinate system (Source: Producer defined)
    Range of values
    Minimum:585380.628
    Maximum:607952.464
    Units:meters
    Northing (m)
    North coordinate of data point relative to the North American Datum of 1983 (2011 realization), projected in the Universal Transverse Mercator (UTM), Zone 10 North, meters, coordinate system (Source: Producer defined)
    Range of values
    Minimum:4073957.261
    Maximum:4092994.107
    Units:meters
    Ellipsoid Height (m)
    Height in meters of data point with reference to the reference ellipsoid (Source: Producer defined)
    Range of values
    Minimum:-84.226
    Maximum:-30.042
    Units:meters
    Orthometric Height (m)
    Height in meters of data point with reference to the North American Vertical Datum of 1988. (Source: Producer defined)
    Range of values
    Minimum:-50.343
    Maximum:3.476
    Units:meters

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
    • Alexander G. Snyder
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Andrew W. Stevens
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Oceanographer
    2885 Mission St.
    Santa Cruz, CA
    USA

    831-460-7424 (voice)
    astevens@usgs.gov

Why was the data set created?

Data were obtained to document changes in shoreline position and coastal morphology as they relate to episodic (storms), seasonal, interannual, and longer (for example, El Niño) processes. 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 topographic and shallow-water 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: 01-Oct-2015 (process 1 of 3)
    Bathymetry data were collected between September 28 and October 1, 2015 using two identical single-beam sonar systems and global navigation satellite systems (GNSS) receivers mounted on personal watercraft (PWC). The sonar systems consisted of an Odom Echotrac CV-100 single-beam echosounder and 200 kHz transducer with a 9-degree beam angle. Raw acoustic backscatter returns were digitized by the echosounder with a vertical resolution of 1.25 cm. Depths from the echosounders were computed using sound velocity profiles measured using a YSI CastAway CTD during the survey. Positioning of the survey vessels was determined at 10-Hz using Trimble R7 GNSS receivers and Zephyr Model 2 antennas operating in autonomous mode. Output from the GNSS receivers and sonar systems were combined in real time on the PWC by a computer running HYPACK hydrographic survey software. Navigation information was displayed on a video monitor, allowing PWC operators to navigate along survey lines at speeds of 2 to 3 m/s.
    Date: 07-Dec-2015 (process 2 of 3)
    Survey-grade positions of the PWCs were achieved with a single-base station and differential post-processing. Positioning data from the GNSS receivers were post-processed using Waypoint Grafnav to apply differential corrections from a GNSS base station with known 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 National Geodetic Survey Geoid12a 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 final point data from the PWCs are projected in cartesian coordinates using the UTM Zone 10 North, meters coordinate system.
    Date: 16-Oct-2017 (process 3 of 3)
    All available bathymetry data from the survey were compiled into a comma-delimited text file for distribution
  3. What similar or related data should the user be aware of?
    International Hydrographic Organization (IHO), 2008, IHO standards for hydrographic surveys (5th ed.): International Hydrographic Bureau Special Publication 44, 28p., Monaco.

    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?
    Survey-grade positions of the personal watercraft (PWCs) were achieved with global navigation satellite system (GNSS) receivers and a single GNSS base station. The position of the GNSS base station was derived from two static GNSS occupations on January 14 and January 16, 2014, with durations of 6 and 3 hours, respectively. The static observations were processed using the National Geodetic Survey Online Positioning User Service (OPUS) and averaged to derive the final base station coordinates relative to the North American Datum of 1983 (2011 realization). Positioning data from the PWCs were post-processed using Waypoint Grafnav to apply differential corrections from the GNSS base station. Manufacturer reported accuracy for the differentially corrected horizontal positions for the GNSS rover trajectories is 0.8 cm + 0.5 ppm. Baselines from the GNSS base station varied between 1.5 km and 29 km with a mean of 13 km, suggesting the average horizontal accuracy of survey vessel positions to be about 1.5 cm. Uncertainty in the horizontal positions associated with pitch and roll of the survey vessels is unknown.
  3. How accurate are the heights or depths?
    Uncertainty in the final elevations is derived from the combination of uncertainty in the GNSS positioning and bathymetric sounding measurements. Manufacturer reported accuracy for the differentially corrected vertical positions for the GNSS rover trajectories is 1.5 cm + 1 ppm. Baselines from the GNSS base station varied between 1.5 km and 29 km with a mean of 13 km, suggesting the average vertical accuracy of survey vessel positions to be about 3 cm. The manufacturer of the single-beam echosounder used in this study reports a vertical accuracy of 1 cm. Additional uncertainty in the final computed elevations data is related to unmeasured variability in the speed of sound used to compute depths from bathymetric soundings and, thus, is depth-dependent. Based on analysis of available speed of sound measurements, we estimate uncertainties in the final depth soundings to be no greater than 1 percent of the water depth. The total vertical uncertainty is calculated using the constant- and depth-dependent factors summed in quadrature (International Hydrographic Organization, 2008). The vertical uncertainty in final elevations varied between 2 cm and 16 cm with a mean vertical uncertainty of 9 cm. Uncertainty in the vertical positions associated with pitch and roll of the survey vessels is unknown.
  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? Bathymetry data are available as a comma-delimited text file (mb15_sept_pwc.csv), 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: 25-Oct-2017
Metadata author:
Andrew W. Stevens
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Oceanographer
2885 Mission St.
Santa Cruz, CA
USA

831-460-7424 (voice)
astevens@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/monterey_bay/mb15_sept_pwc_metadata.faq.html>
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