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Florida Bay 1990 trackline map

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Frequently-anticipated questions:


What does this data set describe?

Title: Florida Bay 1990 trackline map
Abstract:
The map shows the tracklines for bathymetric data collected between 1995 and 1999 for Florida Bay. The areas on the map are linked to the corresponding data sets which contain values for X (easting), Y (northing), Z (elevation), and the RMS computed from Ashtech PNAV software.

The data set is labeled 1990 for easy comparison. The project duration was a decade.

  1. How should this data set be cited?

    Hansen, Mark, 2000, Florida Bay 1990 trackline map: U.S. Geological Survey, Center for Coastal Studies, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -81.11667
    East_Bounding_Coordinate: -80.36667
    North_Bounding_Coordinate: 25.25
    South_Bounding_Coordinate: 24.733333

  3. What does it look like?

    <https://sofia.usgs.gov/publications/ofr/00-347/1990tk.html> (GIF)
    location of 1990's tracklines

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

    Beginning_Date: 1995
    Ending_Date: 1999
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: map

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference: Florida Bay

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 17
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -81
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000
      False_Northing: 0

      Planar coordinates are encoded using Coordinate Pair
      Abscissae (x-coordinates) are specified to the nearest 0.01
      Ordinates (y-coordinates) are specified to the nearest 0.01
      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.
      The flattening of the ellipsoid used is 1/298.257.

      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?

    Entity_and_Attribute_Overview:
    The map shows the lines of data collection and each quad is linked to its corresponding data file.
    Entity_and_Attribute_Detail_Citation: USGS personnel


Who produced the data set?

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

    • Mark Hansen

  2. Who also contributed to the data set?

    Nancy T. DeWitt assisted in the bathymetric surveys and data processing. L. Thornton processed the historical data and provided GIS support.

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

    Mark Hansen
    U.S. Geological Survey
    600 Fourth Street South
    St. Petersburg, FL 33701
    USA

    727 803-8747 x 3036 (voice)
    727 803-2030 (FAX)
    mhansen@usgs.gov


Why was the data set created?

Detailed, high-resolution maps of Florida Bay mudbank elevations are needed to understand sediment dynamics and provide input into water quality and circulation models. The bathymetry of Florida Bay has not been systematically mapped in nearly 100 years, and some shallow areas of the bay have never been mapped. An accurate, modern bathymetric survey provides a baseline for assessing future sedimentation rates in the Bay, and a foundation for developing a sediment budget. Due to the complexity of the Bay and age of existing data, a current bathymetric grid (digitally derived from the survey) is critical for numerical models.

Numerical circulation and sediment transport models being developed for the South Florida Ecosystem Restoration Program are being used to address water quality issues in Florida Bay. Application of these models is complicated due to the complex seafloor topography (basin/mudbank morphology) of the Bay. The only complete topography data set of the Bay is 100 years old. Consequently, an accurate, modern seafloor bathymetry map of the Bay is critical for numerical modeling research. A modern bathymetry data set will also permit a comparison to historical data in order to help access sedimentation rates within the Bay.

The objective of this research was to collect new bathymetry for all of Florida Bay, digitize the historical shoreline and bathymetric data, compare previous data to modern data, and produce maps and digital grids of historical and modern bathymetry.


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: Oct-1999 (process 1 of 1)
    Florida Bay was mapped by using a shallow-draft boat equipped with a high-precision Global Positioning System (GPS) coupled with a high-precision depth sounder. To accomplish this task, SANDS (System for Accurate Nearshore Depth Surveying) was developed by Mark Hansen and Jeff List of the US Geological Survey. SANDS utilizes differential GPS receivers, a digital fathometer, a heave-roll-pitch sensor, and a shallow-draft boat. The SANDS system is accurate to approximately 4 cm horizontally and 8 cm vertically and collects data in water depths as shallow as 30 cm. To achieve this accuracy, the boat's roving distance from any one GPS reference receiver location must be within a 10-kilometer radius.

    Data was collected on a USGS 7.5-minute quadrangle-by-quadrangle basis, proceeding westward from Blackwater Sound. The trackline spacing varied depending upon the relief of the sea floor; that is, closer spacing adjacent to mudbanks and wider spacing in the basins. Tracklines were surveyed in a north-south orientation, and crossings (intersecting tracklines) were surveyed in an east-west orientation. Crossing lines are critical because they served as a check on the accuracy of the system. In theory, data values at the crossing should be exactly the same. In reality, this is not always the case due to random errors of each sensor. Eighty-five percent of the crossings in this data set were within +/- 6 cm with the balance within +/- 20 cm.

    Ideally, crossings are made at the end of the survey day; however, some of the crossings were made months and even years after an area was initially surveyed. The results are very good considering the soft bottom characteristics of Florida Bay. Bathymetric positions for this study were derived using differential GPS techniques on 10-km baselines or less. One or more GPS reference stations (base stations) were continuously recording full-phase carrier data while the boat surveyed. A rover GPS receiver on the boat was simultaneously recording carrier information.

    Record epoch interval was 1 second for both base station and rover receivers. Precise positions for each epoch were computed using Ashtech Precise Differential GPS Navigation and Surveying (PNAV) v2.0 software. PNAV provides a root mean squared (RMS) value for each epoch. For this study, a RMS value of 0.08 cm or less was considered reasonable. An RMS value of 1.0 indicates that the GPS data ambiguities were unresolved, and that the depths were determined by a tie-line best-fit method. For data format consistencies, RMS values for the 1890's data set are equal to 0.0. The horizontal positions of each data point were transformed from Latitude/Longitude to UTM (Zone 17) XY coordinates using NOAA/NGS software UTMSv1.0. Vertical positions were converted from ellipsoid height to orthometric height using NOAA/NGS software GEOID96, where orthometric height is considered to be equal to NAVD88. According to NOAA tidal datum information, NAVD88 is approximately 0.41m (1.35 ft) above MLW in the Florida Bay area. The 1.35 feet average is calculated using the elevation information from several tidal benchmarks throughout the Florida Keys. These tidal benchmarks are published by the National Geodetic Survey and can be located on their website <http://www.ngs.noaa.gov/cgi-bin/ngs_opsd.prl/>. Five tidal benchmarks were chosen from four different U.S. Geological Quadrangle locations including Blackwater Sound, Plantation Key, Long Key and Grassy Key. To compare this data set with other depth information, which is relative to MLW, e.g. NOAA nautical charts, 0.41 m (1.35 ft) is algebraically subtracted from each depth value or contour line.

    Geodetic control in Florida Bay was lacking in number and geometric strength. In order to accomplish centimeter vertical accuracy, additional geodetic control needed to be established within the Bay. Thirteen new temporary ground-control points or benchmarks (surveyed to within 1 cm to 2 cm accuracy) were established throughout the Bay for use as reference receiver sites. The thirteen benchmarks were surveyed using Ashtech Z-12, 12 channel dual-frequency GPS receivers. Full-phase carrier data were recorded on each occupied benchmark in Ashtech proprietary BIN format with daily occupations ranging from 6 to 12 hours. BIN files were then converted to RINEX-2 format and position determined by the National Aeronautics and Space Administrations (NASA) Jet Propulsion Laboratory GIPSY system software. The GIPSY derived positions were provided in ITRF96 coordinate system for each (daily) occupation. Using National Oceanic and Atmospheric Administration/National Geodetic Survey (NOAA/NGS) software HTDPv2.3, ITRF96 positions were transformed to NAD83/GRS80 positions. The computed daily positions were then averaged to derive a final benchmark location and elevation. Daily outliers greater than 0.05cm (in the vertical component) from the average were not included in the final average.

    Person who carried out this activity:

    Nancy DeWitt
    U.S. Geological Survey
    Marine Geologist
    600 Fourth Street South
    St. Petersburg, FL 33701
    USA

    727 803-8747 ext. 3058 (voice)
    727 803-2030 (FAX)
    ndewitt@usgs.gov

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

    Hansen, Mark DeWitt, Nancy T., 2000, 1890 and 1990 Bathymetry of Florida Bay: USGS Open-File Report OFR 00-347, U.S. Geological Survey, St. Petersburg, FL.

    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?

    For data format consistencies, RMS values for the 1890's data set are equal to 0.0. The horizontal positions of each data point were transformed from Latitude/Longitude to UTM (Zone 17) XY coordinates using NOAA/NGS software UTMSv1.0.

  3. How accurate are the heights or depths?

    Vertical positions were converted from ellipsoid height to orthometric height using NOAA/NGS software GEOID96, where orthometric height is considered to be equal to NAVD88.

    According to NOAA tidal datum information, NAVD88 is approximately 0.41m (1.35 ft) above MLW in the Florida Bay area. The 1.35 feet average is calculated using the elevation information from several tidal benchmarks throughout the Florida Keys. These tidal benchmarks are published by the National Geodetic Survey and can be located on their website <http://www.ngs.noaa.gov/cgi-bin/ngs_opsd.prl/>. Five tidal benchmarks were chosen from four different U.S. Geological Quadrangle locations including Blackwater Sound, Plantation Key, Long Key and Grassy Key. The open-file report contains a table for quick reference of information for the five tidal benchmarks.

    To compare this data set with other depth information which is relative to MLW, e.g. NOAA nautical charts, 0.41 m (1.35 ft) is algebraically subtracted from each depth value or contour line.

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

    All data were processed and used to generate the bathymetric data points.

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

    not applicable


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:
The U.S. Geological Survey must be referenced as the originator of the data set in any future products or research derived from these data.

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

    Heather S.Henkel
    U.S. Geological Survey
    600 Fourth St. South
    St. Petersburg, FL 33701
    USA

    727 803-8747 ext 3028 (voice)
    727 803-2030 (FAX)
    hhenkel@usgs.gov

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

    Florida Bay 1990's trackline map

  3. What legal disclaimers am I supposed to read?

    The data have no implied or explicit guarantees

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 11-Jun-2007
Metadata author:
Heather Henkel
U.S. Geological Survey
600 Fourth Street South
St. Petersburg, FL 33701
USA

727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
sofia-metadata@usgs.gov

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


This page is <https://sofia.usgs.gov/metadata/sflwww/hansen_1990_trackline_map.faq.html>

U.S. Department of the Interior, U.S. Geological Survey
Comments and suggestions? Contact: Heather Henkel - Webmaster
Generated by mp version 2.8.18 on Mon Jun 11 15:42:37 2007