St. John Shallow Water Accuracy Assessment Transects

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Frequently anticipated questions:

What does this data set describe?

Title: St. John Shallow Water Accuracy Assessment Transects
Abstract:
Benthic habitat maps of the nearshore marine environment of St. John, U.S. Virgin Islands were created by visual interpretation of remotely sensed imagery. The objective of this effort, conducted by NOAA's Center for Coastal Monitoring and Assessment - Biogeography Branch in partnership with the U.S. National Park Service (NPS), was to provide spatially-explicit information on the habitat types, biological cover and live coral cover of St. John's coral reef ecosystem. The data described herein represent accuracy assessment (AA) sites explored by NOAA field scientists to evaluate the thematic accuracy of the benthic habitat maps of St. John. Considering vessel drift during habitat characterization, the entire evaluation period was most accurately represented by a series of GPS points logged at five-second intervals.
Supplemental_Information:
Data were collected on 486 ground validation sites over a two-week field mission from February 9-20, 2009 aboard U.S. National Park Service small research vessels. As anchoring at each site was not feasible for rapid assessment, wind and wave effects caused the survey vessel to drift along a transect. Post-processing of the GPS data allowed for a series of points to represent the actual survey location.
  1. How might this data set be cited?
    Laurie Bauer, NOAA/NOS/NCCOS/CCMA Biogeography Branch, 2009, St. John Shallow Water Accuracy Assessment Transects: NOAA's Ocean Service, National Centers for Coastal Ocean Science (NCCOS), Silver Spring, MD.

    Online Links:

    Other_Citation_Details:
    Please use citation for the written document "Benthic Habitats of St. John, U.S. Virgin Islands" when using these data.
    This is part of the following larger work.

    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA), Biogeography Program, 2009, Benthic Habitats of St. John, U.S. Virgin Islands: NOAA National Centers for Coastal Ocean Science, Silver Spring, MD.

    Other_Citation_Details:
    Zitello, A.G., L.J. Bauer, T.A. Battista, P.W. Mueller and M.S. Kendall. 2009. Benthic Habitats of St. John, U.S. Virgin Islands. NOAA Technical Memorandum NOS NCCOS 96. 50 pp.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -64.839479
    East_Bounding_Coordinate: -64.645648
    North_Bounding_Coordinate: 18.374291
    South_Bounding_Coordinate: 18.297031
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 09-Feb-2009
    Ending_Date: 20-Feb-2009
    Currentness_Reference: ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Entity Point (5785)
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 20
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -63.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using Coordinate Pair
      Abscissae (x-coordinates) are specified to the nearest 0.000001
      Ordinates (y-coordinates) are specified to the nearest 0.000001
      Planar coordinates are specified in meters
      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 1/298.257224.
  7. How does the data set describe geographic features?
    St. John Accuracy Assessment Transects
    Shapefile attribute table (Source: None)
    FID
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: ESRI) Coordinates defining the features.
    Max_PDOP
    Maximum Positional Dilution of Precision (Source: Automatically generated by Trimble) Unknown
    Max_HDOP
    Maximum Horizontal Dilution of Precision (Source: Automatically generated by Trimble) Unknown
    GPS_Date
    Date of logged position (Source: Automatically generated by Trimble)
    Range of values
    Minimum:2009 February 9
    Maximum:2009 February 20
    GPS_Time
    Time of logged position (Source: Automatically generated by Trimble)
    Range of values
    Minimum:06:00:00am
    Maximum:06:00:00pm
    Vert_Prec
    Vertical Precision (Source: Automatically generated by Trimble) in meters
    Horz_Prec
    Hortizontal Precision (Source: Automatically generated by Trimble) in meters

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?
    Tim Battista
    NOAA National Ocean Service
    Researcher
    1305 East West Highway
    Silver Spring, MD
    USA

    (301) 713-3028 x171 (voice)
    (301) 713-4388 (FAX)
    Tim.Battista@noaa.gov

Why was the data set created?

The purpose of this survey data was to collect information on current habitat conditions at random locations throughout the mapping area. Locations were determined by an iterative, GIS-based, stratified random sampling technique to ensure that all bottom classifications would be assessed. This information was used to evaluate the thematic accuracy of the St. John benthic habitat map.

How was the data set created?

  1. From what previous works were the data drawn?
    Trimble SSF files (source 1 of 1)
    NOAA, 2009, GPS data.

    Type_of_Source_Media: GPS data
    Source_Contribution:
    GPS data, which were originally recorded as code-phase signals in Trimble SSF format, were differentially post-processed to the Continually Operating Reference System (CORS) station at St. Thomas, U.S. Virgin Islands (VITH).
  2. How were the data generated, processed, and modified?
    Date: 2009 (process 1 of 4)
    A benthic habitat map was generated from delineating features by visual inspection of remotely sensed imagery and incorporation of field data acquired during a ground validation mission. Target locations for the accuracy assessment of this habitat map were determined by an iterative, GIS-based, stratified random sampling technique to ensure that all bottom classifications would be assessed. Based on guidelines from other recent accuracy assessment analyses (Battista et al. 2007), a minimum of 25 points were assigned to each of the 13 detailed structure classes within the draft habitat map. An additional 175 points were distributed based on the proportion of area of each structure class in the map. Points were randomly placed within each class using Hawth's Analysis Tools (Beyer 2004) in ArcGIS at a minimum distance of 50 m apart. Next, the number of points that fell within each detailed primary cover class was calculated. Where necessary, additional points were randomly added and re-distributed from classes with many points to ensure that there was a minimum of 25 points within each detailed cover class.

    Process Dates: 2008-2009 Person who carried out this activity:

    Laurie Bauer
    NOAA/NOS/NCCOS/CCMA Biogeography Branch
    1305 East West Highway
    Silver Spring, MD
    U.S.A.

    (301) 713 - 3028 (voice)
    Date: 2009 (process 2 of 4)
    NOAA field scientists explored the accuracy assessment locations with a suite of assessment techniques depending on the conditions at each site. A combination of underwater video (primary method), free diving, snorkeling and surface observations were used to survey the ecological characteristics at each location.

    At the start of every morning, the boat captain selected a general region to begin the day's work. Navigating to field locations was accomplished using a Garmin GPS 76 device with the uploaded GV site coordinates. The boat captain maneuvered the vessel to within 5 m of the target location and made every effort to maintain that location without jeopardizing crew and equipment safety. Once on site, NOAA scientists would simultaneously deploy a SeaViewer Sea-Drop 950 camera and begin logging a waypoint on a Trimble GeoXT GPS receiver.While the video camera was capturing bottom imagery, an observer viewed the video real-time on a Panasonic Toughbook aboard the survey vessel. They categorized each site according to the levels of the habitat classification scheme: major and detailed geomorphological structure, major biological cover, percent major biological cover and percent coral cover. Data was entered into a custom data dictionary generated in Trimble Pathfinder Office software and loaded onto the Trimble data logger. Person who carried out this activity:

    Laurie Bauer
    NOAA/NOS/NCCOS/CCMA Biogeography Branch
    1305 East West Highway
    Silver Spring, MD
    U.S.A.

    (301) 713 - 3028 (voice)
    Date: 2009 (process 3 of 4)
    Trimble Pathfinder Office software was used to post process and differentially correct the raw GPS data to the Continually Operating Reference System (CORS) station at St. Thomas, U.S. Virgin Islands (VITH). All positions acquired for a single site were plotted to represent the entire duration of bottom evaluation as the boat drifted. Person who carried out this activity:
    Tim Battista
    NOAA National Ocean Service
    Researcher
    1305 East West Highway
    Silver Spring, MD
    USA

    (301) 713-3028 x171 (voice)
    (301) 713-4388 (FAX)
    Tim.Battista@noaa.gov
    Date: 2009 (process 4 of 4)
    Ultimately, precisely positioned GPS positions, the evaluation transect and the associated classification data were viewed in a GIS to assess the accuracy of the draft benthic habitat map. Person who carried out this activity:
    Laurie Bauer
    NOAA/NOS/NCCOS/CCMA Biogeography Branch
    1305 East West Highway
    Silver Spring, MD
    U.S.A.

    (301) 713 - 3028 (voice)
  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 points in this data layer were acquired by GPS data using a Trimble GeoXT receiver. All data point characteristics were recorded in the GPS data logger automatically and seamlessly transferred to ArcGIS shapefiles using Trimble Pathfinder Office software. Attributes are all expected to be correct.
  2. How accurate are the geographic locations?
    The true positional accuracy of individual epics was determined to be within 1 m for 96% of the logged points. However, it is estimated that horizontal accuracies may be 0 - 20m from the true position of the underwater camera assessment due to line "lay-back" during drift.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    486 field positions were occupied and habitat characterizations were conducted for accuracy assessment during this work. A small subset of the accuracy assessment sites did not have transect information in this dataset, depending on the evaluation technique. Snorkel and visual inspection from distances did not allow for a GPS receiver to occupy the exact location, as a result, approximated GPS locations were used instead without the opportunity for transects with the underwater camera.
  5. How consistent are the relationships among the observations, including topology?
    Data points were collected with mapping-grade GPS receivers. The data were post processed for differential correction to the Continually Operating Reference System (CORS) station at St. Thomas, U.S. Virgin Islands (VITH).

    All attribute information was recorded by the GPS receiver and stored directly in the raw GPS files. This automated process was assumed to be error free. This file is believed to be logically consistent.

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: Not for navigation.
  1. Who distributes the data set? (Distributor 1 of 1)
    National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA), Biogeography Program
    1305 East West Highway
    Silver Spring, MD

    301-713-3028 x171 (voice)
    301-713-4384 (FAX)
    tim.battista@noaa.gov
    Hours_of_Service: 0800 - 1700, Monday to Friday, EST
  2. What's the catalog number I need to order this data set? Downloadable Data
  3. What legal disclaimers am I supposed to read?
    The National Oceanic and Atmospheric Administration (NOAA) National Centers for Coastal Ocean Science (NCCOS) is publishing this data on their website. NCCOS Biogeography Branch does not guarantee the accuracy of the geographic features or attributes. Please see the written report and metadata records for each data set for complete information on the source, limitations, and proper use.
  4. How can I download or order the data?
  5. Is there some other way to get the data?
    Contact NOAA for distribution options (see Distributor).

Who wrote the metadata?

Dates:
Last modified: 29-Mar-2020
Last Reviewed: 15-Mar-2010
Metadata author:
National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA), Biogeography Branch
Primary Map Creator
1305 East West Highway
Silver Spring, MD

301-713-3028 (voice)
301-713-4384 (FAX)
Hours_of_Service: 0800 - 1700, Monday to Friday, EST
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Generated by mp version 2.9.48 on Fri Apr 19 11:01:36 2024