Benthic Habitats of Puerto Rico and the U.S. Virgin Islands; Photomosaic of U.S. Virgin Islands (St. John), 1999

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Frequently anticipated questions:


What does this data set describe?

Title:
Benthic Habitats of Puerto Rico and the U.S. Virgin Islands; Photomosaic of U.S. Virgin Islands (St. John), 1999
Abstract:
Habitat maps of Puerto Rico and the U.S. Virgin Islands were created by visual interpretation of aerial photographs using the Habitat Digitizer Extension. Aerial photographs are valuable tools for natural resource managers and researchers since they provide an excellent record of the location and extent of habitats. However, spatial distortions in aerial photographs due to such factors as camera angle, lens characteristics, and relief displacement must be accounted for during analysis to prevent incorrect measurements of area, distance, and other spatial parameters.

These distortions of scale within an image can be removed through orthorectification. During orthorectification, digital scans of aerial photos are subjected to algorithms that eliminate each source of spatial distortion. The result is a georeferenced digital mosaic of several photographs with uniform scale throughout the mosaic. Features near land are generally georeferenced with greater accuracy while the accuracy of features away from land is generally not as good. Where no land is in the original photographic frame only kinematic GPS locations and image tie points were used to georeference the images. After the orthorectified mosaics were created, photointerpreters were able to accurately and reliably delineate boundaries of features in the imagery as they appear on the computer monitor.

  1. How should this data set be cited?

    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Environmental Satellite Data, and Information Service (NESDIS), National Geophysical Data Center (NGDC), 20010501, Benthic Habitats of Puerto Rico and the U.S. Virgin Islands; Photomosaic of U.S. Virgin Islands (St. John), 1999: NOAA's National Geophysical Data Center (NGDC), Boulder, CO.

    Online Links:

    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, 20011201, Benthic Habitat Maps of Puerto Rico and the U.S. Virgin Islands Prepared by Visual Interpretation from Remote Sensing Imagery Collected by NOAA Year 1999: NOAA's Ocean Service, National Centers for Coastal Ocean Science (NCCOS), Silver Spring, MD.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -64.82
    East_Bounding_Coordinate: -64.64
    North_Bounding_Coordinate: 18.38
    South_Bounding_Coordinate: 18.29

  3. What does it look like?

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

    Calendar_Date: Feb-1999
    Currentness_Reference: publication date

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

    Geospatial_Data_Presentation_Form: raster digital data

  6. How does the data set represent geographic features?

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

      This is a Raster data set.

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

      The map projection used is Transverse Mercator.

      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -63
      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 2.4
      Ordinates (y-coordinates) are specified to the nearest 2.4
      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.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    Pixel values are MrSID compressions. Data were originally geoTIFF format.
    Entity_and_Attribute_Detail_Citation:
    MrSID Compressed orthorectified images; UTM Zone 20.


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?

    National Geophysical Data Center

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

    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
    Biogeography Team Leader, Mapping Manager
    1305 East West Highway, N/SCI-1
    Silver Spring, MD 20910

    301-713-3028 (voice)
    301-713-4388 (FAX)
    matt.kendall@noaa.gov

    Hours_of_Service: 0800-1700, Monday to Friday, EST


Why was the data set created?

The National Ocean Service is conducting research to digitally map biotic resources and coordinate a long-term monitoring program that can detect and predict change in U.S. coral reefs, and their associated habitats and biological communities.


How was the data set created?

  1. From what previous works were the data drawn?

    NOAA/NOS/NGS Aerial Photos (source 1 of 1)
    National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), National Geodetic Survey (NGS), 1999, National Geodetic Survey Aerial Photography of Puerto Rico and the U.S. Virgin Islands, 1999: NOAA's Ocean Service, National Geodetic Survey (NGS), Silver Spring, MD.

    Online Links:

    Type_of_Source_Media: aerial photography and scanned photos
    Source_Scale_Denominator: 48000
    Source_Contribution:
    NOS aerial photos were used to create orthophoto mosaics

  2. How were the data generated, processed, and modified?

    Date: 2000 (process 1 of 1)
    Aerial photographs were acquired for Puerto Rico and the U.S. Virgin Islands Benthic Mapping Project in 1999 by NOAA Aircraft Operation Centers aircraft and National Geodetic Survey cameras and personnel. Approximately 600, color, 9 by 9 inch photos were taken of the coastal waters of Puerto Rico and the U.S. Virgin Islands at 1:48000 scale. Specific sun angle and maximum percent cloud cover restrictions were adhered to when possible during the photography mission to ensure collection of high quality imagery for the purpose of benthic mapping.

    Print and diapositives were created from the original negatives. Diapositives were then scanned at a resolution of 500 dots per inch (DPI) using a metric scanner, yielding 2.4 by 2.4 meter pixels for the 1:48000 scale photography. All scans were saved in TIFF format for the purposes of orthorectification and photointerpretation.

    Georeferencing/mosaicing of the TIFF's was performed using Socet Set Version 4.2.1. Lens correction parameters were applied to each frame to eliminate image distortion. Airborne kinematic GPS was then used when available to provide a first order geolocation. When this information was not available, measurements were made between flightline strips for input into Socet Set to provide preliminary co-registration.

    Image to image tie-points were then used to further co-register the imagery, especially for photos taken over open water where ground control points were not available. Fixed ground features visible in the scanned photos were selected for ground control points (GCP's) which were then used to georeference the imagery. GCP's were measured using real-time DGPS (differential Global Positioning System). Points were obtained with a wide distribution throughout the imagery, especially on peninsulas and outer islands whenever possible since this results in the most accurate registration throughout each image. Only ground control points for terrestrial features were collected due to difficulty of obtaining precise positions for submerged features.

    A custom digital terrain model (DTM) was then created using the Socet Set software to correct for feature displacement due to terrain effects. To accomplish this, water features and the shoreline were set to an elevation of zero. Preliminary experimentation revealed that the effects of refraction on the position of submerged features in the imagery were not significant enough to make a correction for underwater displacement according to Snell's law. Selected land elevation points were then inserted from USGS 1:24000 Digital Elevation Models or other elevation data sets where clouds or other sources of interference prevented the Socet Set software from automatically making an accurate DTM.

    Once the terrain models were complete and a draft orthorectified mosaic was produced, a set of independent ground control points was used to measure the quality of each mosaic's rectification and ensure that it met acceptable limits of horizontal spatial accuracy. If spatial accuracy was not acceptable based on this comparison, additional modifications were made, until a satisfactory mosaic was created for each island. In general, mosaics were georeferenced such that pixels are positioned within one pixel width of their correct location.

    Person who carried out this activity:

    National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA), Biogeography Program
    Biogeography Team Leader, Mapping Manager
    1305 East West Highway, N/SCI-1
    Silver Spring, MD 20910

    301-713-3028 (voice)
    301-713-4388 (FAX)
    matt.kendall@noaa.gov

    Hours_of_Service: 0800-1700, Monday to Friday, EST
  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?

  2. How accurate are the geographic locations?

    Horizontal accuracy was determined by solution of Socet Set generated model (RMS less than 1) and by comparison to independent ground control data. x=1.4 +/-1.3, y=1.1 +/-3.4 values are in meters +/- standard deviation

  3. How accurate are the heights or depths?

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

    No color balancing was attempted since this alters color and textural signatures in the original imagery and interferes with the photointerpreter's ability to delineate habitats. As a result mosaics have visible seams between adjacent photos. This provides the photointerpreter with "true color" imagery for maximum ability to identify and delineate benthic features.

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

    Once all of the photographs were orthorectified, the best segments of each photograph were selected for creation of the final mosaic. Segments of each photograph were selected to minimize sun glint, cloud interference, and turbidity in the final mosaic. Where possible, parts of images obscured by sun glint or clouds were replaced with cloud/glint free parts of overlapping images. As a result, most mosaics have few or no clouds or sun glint obscuring bottom features.


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: none

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

    National Atmospheric and Oceanic Administration (NOAA), National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA), Biogeography Program
    Biogeography Team Leader, Mapping Manager
    1305 East West Highway N/SCI-1
    Silver Spring, MD 20910

    301-713-3028 (voice)
    301-713-4388 (FAX)
    matt.kendall@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?

    Data are not to be used for navigation. Disclaimer- While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 17-Dec-2012
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 Program
Biogeography Team Leader, Mapping Manager
1305 East West Highway, N/SCI-1
Silver Spring, MD 20910

301-713-3028 (voice)
301-713-4388 (FAX)
matt.kendall@noaa.gov

Hours_of_Service: 0800-1700, Monday to Friday, EST
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)


Generated by mp version 2.9.13 on Fri Apr 18 10:40:20 2014