Evaluation of a single-beam sonar system to map seagrass at two sites in northern Puget Sound

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Frequently-anticipated questions:


What does this data set describe?

Title:
Evaluation of a single-beam sonar system to map seagrass at two sites in northern Puget Sound
Abstract:
Nearshore bathymetry and seagrass cover at two sites in northern Puget Sound were mapped with single-beam sonar and an underwater video. Acoustic data were compared against underwater video data collected simultaneously to better understand the accuracy, limitations and benefits of mapping seagrass acoustically in Puget Sound.
Supplemental_Information:
To map seagrass at two sites in northern Puget Sound, a dual-frequency Biosonics sonar operating at 200 and 430 kHz was used to map seafloor depth, morphology and vegetation. An underwater video camera was deployed to ground-truth acoustic data. Fifty one sediment samples were collected to quantify sediment grain size distributions across Possession Point. Sediment samples were analyzed for grain size at the Western Coastal and Marine Geology Team sediment laboratory in Menlo Park, CA.
  1. How should this data set be cited?

    Stevens, A.W., Lacy, J.R., Finlayson, D.P., an, 2008, Evaluation of a single-beam sonar system to map seagrass at two sites in northern Puget Sound:.

    This is part of the following larger work.

    Stevens, A.W., Lacy, J.R., Finlayson, D.P., an, 2008, Evaluation of a single-beam sonar system to map seagrass at two sites in northern Puget Sound: Scientific Investigations Report 2008-5009, U.S. Geological Survey, Coastal and Marine Geology Program, Menlo Park, CA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -123.17290
    East_Bounding_Coordinate: -123.13793
    North_Bounding_Coordinate: 48.60642
    South_Bounding_Coordinate: 48.58775

  3. What does it look like?

    <http://walrus.wr.usgs.gov/infobank/b/b207ps/html/b-2-07-ps.meta.html> (GIF)
    Index map of field activity B-2-07-PS.

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 30-Jan-2007
    Ending_Date: 02-Feb-2007
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: tabular digital data

  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.

    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 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.1
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
      Depth_System_Definition:
      Depth_Datum_Name: local surface
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    line[number].xyz
    digital surface elevation data (Source: USGS)

    X
    Location X-coordinate of the data point. (Source: USGS)

    Range of values
    Minimum:486997.617
    Maximum:489962.263
    Units:meters
    Resolution:0.001

    Y
    Location Y-coordinate of the data point. (Source: USGS)

    Range of values
    Minimum:5381456.319
    Maximum:5383932.558
    Units:meters
    Resolution:0.001

    Z
    Location Z-coordinate of the data point. (Source: USGS)

    Range of values
    Minimum:-10.00
    Maximum:0.00
    Units:meters
    Resolution:0.01

    sediment grain size data
    surface elevation data (Source: USGS)

    Lon
    Location X-coordinate of the data point. (Source: USGS)

    Range of values
    Minimum:-123.58611
    Maximum:-123.13611
    Units:decimal degrees
    Resolution:0.00001

    Lat
    Location Y-coordinate of the data point. (Source: USGS)

    Range of values
    Minimum:48.58611
    Maximum:48.60833
    Units:decimal degrees
    Resolution:0.00001

    Depth_m
    Location Z-coordinate of the data point. (Source: USGS)

    Range of values
    Minimum:0.00
    Maximum:10.00
    Units:meters
    Resolution:0.01

    Entity_and_Attribute_Overview:
    Sample of digital surface elevation data XYZ ASCII file, bathy/line95.xyz:
    X             Y              Z
    487989.879521 5381998.198351 -3.31
    487990.116289 5381998.892258 -3.34
    487989.943243 5382001.029467 -3.40
    
    Sample of sediment sampling log:
    Station Local_Time       UTC           Lon             Lat           Depth_m    Comment
    1    6/1/07 20:44    6/2/07    3:44    -123.1430877    48.60642247    2.286     -
    2    6/1/07 20:35    6/2/07    3:35    -123.1416559    48.60596625    2.1336    18.6 C
    3    6/1/07 20:28    6/2/07    3:28    -123.1396819    48.60476647    2.4384    22.4 C
    
    Entity_and_Attribute_Detail_Citation: none


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Andrew Stevens
    U.S. Geological Survey, Coastal and Marine Geology
    Oceanographer
    345 Middlefield R. MS999
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5243 (voice)
    (650) 329-5190 (FAX)
    astevens@usgs.gov


Why was the data set created?

The goal of the project was two-fold: 1) To quantify eelgrass (Z. marina) habitat at two sites, Possession Point and Browns Bay, in northern Puget Sound and 2) Evaluate the benefits and limitations of using acoustics, specifically single-beam sonar, to map seagrass in Puget Sound.


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: 2007 (process 1 of 2)
    A) Bathymetric mapping

    The combined bathymetric data were merged to create a digital elevation model representing the surface topography of Possession Point and Browns Bay. This surface is referenced to the NAD83 datum in the WA State Plane North, meters projection with a horizontal accuracy of 2.3 cm. Elevations are referenced to NAVD88 with an estimated vertical accuracy ranging 2.6-9.8 cm. This includes error from the RTK-DGPS and Biosonics sonar, and errors introduced in data processing.

    Date: 2007 (process 2 of 2)
    B) Sediment Samples for Grain Size Analyses

    Results from the tubes and laser particle analyzer were merged using standard USGS methods found in the USGS particle analysis program pcSedSize.

  3. What similar or related data should the user be aware of?

    U.S. Geological Survey, Coastal and Marine Geology Program, 2007, InfoBank.

    Online Links:


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    A) Bathymetric mapping

    Sixty (60) kilometers of acoustic bathymetry/substrate data were collected with a dual-frequency (200 and 430 kHz) Biosonics system along 163 transects in Possession Point between 1/30/07 and 2/1/07. Eighteen(18) kilometers of acoustic bathymetry/substrate data were collected with the same system along 65 transects in Browns Bay on 2/2/2007. The Biosonics sonar generates a 6-degree cone of sound, which translates into a footprint on the seafloor ranging 0.55 to 55 m^2 area for the water depths surveyed (2 - 20 m). Ship speed generally ranged 4.0-4.5 kts and data were merged with GPS positions at 1 Hz. Track lines were spaced 25 - 50 m apart.

    B) Sediment Samples for Grain Size Analyses

    Sediment samples were collected using a van veen grab sampler or taken directly during low-tide surveys.

    In the field, a sub-sample of the uppermost 1-3 cm of each grab was collected and placed into storage bags, labeled, and logged.

    Samples were disaggregated and sieved through 2000 and 62 micron screens to separate gravel, sands and mud after the organic component was removed by treatment with hydrogen peroxide. Sediment grain size of sands was determined using the settling methods and principles of Stokes Law on the USGS 3-m long settling tubes. The fine fraction (silts and clays) were analyzed on a Coulter 230 Laser Particle Analyzer. Three samples had less than 3% intermediate fraction and were analyzed on the Coulter. Single sample runs were made on the tubes, while results from the laser particle analyzer are averages of triplicates with standard deviations around the mean ranging 18 to 24 microns due to instrument errors.

  5. How consistent are the relationships among the observations, including topology?

    A) Bathymetric mapping


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:
Public domain data from the U.S. government is freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.

  1. Who distributes the data set? (Distributor 1 of 1)

    U.S. Geological Survey, Coastal and Marine Geology
    c/o Andrew Stevens
    Oceanographer
    345 Middlefield Rd. MS999
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5243 (voice)
    (650) 329-5190 (FAX)
    astevens@usgs.gov

  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    Although this data set has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.

    Any use of trade, product, or firm 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: 12-Feb-2008
Metadata author:
U.S. Geological Survey, Coastal and Marine Geology
c/o Andrew Stevens
Oceanographer
345 Middlefield Rd. MS999
Menlo Park, CA 94025-3561
USA

(650) 329-5243 (voice)
(650) 329-5190 (FAX)
astevens@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)


Generated by mp version 2.8.11 on Tue Feb 12 13:38:16 2008