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.
This product provides a fine-scale assessment of the status, abundance, and distribution of marine habitats of St. John. The NOAA effort provides the U.S. National Park Service with increased technical capacity for ocean exploration, management, and stewardship. Direct implications to management measures include evaluation of management efficacy, a spatial framework for improved monitoring sampling design, improved assessment of human-use impacts, and marine spatial planning to support alternative marine protected area boundary alternatives.
ground condition
Not for navigation.
1305 East West Highway
A comprehensive assessment was conducted to evaluate the thematic accuracy of the St. John benthic habitat map. Thematic accuracy was characterized for major and detailed geomorphological structure, major and detailed biological cover, and percent coral cover. The independent accuracy assessment revealed successful overall map accuracies of over 90% for major structure and cover classes, and over 80% for detailed structure and cover classes. The 85.7% accuracy achieved for detailed structure in NOAA's new St. John benthic habitat maps were similar to that of other recent NOAA benthic habitat maps in the Florida Keys (86.2%), Palau (90.0%), and the Main Hawaiian Islands (90.0%).
True-color digital orthophotography obtained with an ADS40 digital sensor was the primary imagery source used for delineating benthic habitats of St. John. Orthophotography provided by 3001, Inc., on contract to the U.S. Army Corps of Engineers, was obtained in September and October of 2007 with a one foot ground sample distance (GSD), flight height of 8,650 feet, and 30% sidelap. At limited locations throughout the mapping area, the digital orthophotography was not suitable for habitat delineation; in which case, IKONOS multispectral satellite imagery was used as a replacement. IKONOS satellite imagery was geo-positioned , pan sharpened and deglinted by NOAA. During the digitizing process, image stretches and manipulating image contrast, brightness and color balance were performed in ArcGIS to enhance features in the processed imagery. GIS topologic quality was established by executing ArcGIS extension routines that check for: overlapping polygons, multipart polygons, sliver polygons and void polygons. Additionally checks for adjacent polygons with the same habitat attributes were completed. All errors were identified and corrected. This file is believed to be logically consistent.
Delineation of all habitat boundaries was conducted with the image scale at 1:2,000. This ensured that the level of detail produced by the photo interpreter was uniform throughout the project. The minimum mapping unit (MMU) for identifying habitats or features was 1,000 square meters. The software utilized in this project was designed to alert the photo interpreter each time a polygon was drawn smaller than the a MMU; at which point the polygon was then aggregated with the most logical adjacent polygon.
3001, Inc., the imagery acquiring firm, reported 1:4,800 scale RMSE accuracy of 1.25 m for the orthophotography, but NOAA calculations with known ground control locations resulted in RMSE accuracy of 2.15 m. It is believed that polygon horizontal accuracies are inherited from the source imagery.
This section of the report describes the habitat classification scheme used to classify habitat features. The St. John habitat classification scheme defines benthic communities on the basis of four primary coral reef ecosystem attributes: 1) broad geographic zone, 2) geomorphological structure type, 3) dominant biological cover, and 4) degree of live coral cover.
This ArcGIS extension was used to digitize and attribute benthic zones, structure and biological cover of this map.
Used to identify and digitize benthic habitats of St. John, USVI.
1) Imagery Acquisition - The first step in map creation was the acquisition and processing of a comprehensive dataset of remotely sensed imagery. All imagery was geo-positioned to ensure acceptable spatial accuracy in the mapping product. In the case of St. John, two separate data types were used (color orthophotography and IKONOS satellite imagery) in order to capture the full mappable extent using optical techniques. Process_Contact: Tim A. Battista (NOAA/NOS/NCCOS/CCMA Biogeography Branch)
2) Habitat Boundary Delineation - A first draft benthic habitat map was generated by delineating all features that could be identified by visual inspection of the remotely sensed imagery. During the creation of this first draft, the interpreter placed discrete points on the map that were difficult to distinguish and that warranted further field investigation. These sites were labeled as "ground validation" positions. Process_Date: 2008-2009
3) Ground Validation - NOAA field scientists explored the ground validation locations with a suite of assessment techniques depending on the conditions at each site. A combination of underwater video, free diving, snorkeling and surface observations were used to survey the ecological characteristics at each location. This information was analyzed and the initial maps were edited to generate a second draft map.
4) Expert Review - The draft map was then reviewed by local marine biologists, coral reef scientists and resource managers at a one-day workshop in Cruz Bay, St. John. Comments were integrated into the map products to generate a final draft map.
5) Accuracy Assessment - An independent team of NOAA scientists not associated with map creation, conducted field investigations at pre-defined locations to assess the accuracy of the final draft map. Locations were generated with a stratified random sampling design that allowed for a statistically rigorous assessment of map accuracy. Process_Contact: Laurie J. Bauer (NOAA/NOS/NCCOS/CCMA Biogeography Branch)
6) Final Products Creation - A final benthic habitat map for St. John was generated by correcting inaccuracies elucidated by the accuracy assessment. Additionally, all associated datasets, including GIS files, field video and metadata were packaged and provided to project partners and the public.
Internal feature number.
ESRI
Feature geometry.
A distinct identifier used to define each unique combination of habitat characteristics
NOAA
Calculated feature area
Calculated feature perimeter
Geographic zone
Refer to Chapter 1: Benthic Habitat Classification Scheme of "Benthic Habitats of St. John, U.S. Virgin Islands" (Zitello et al. 2009)
Major Geomorphological Structure
Detailed Geomorphological Structure
Major Biological Cover
Percent Patchiness of Major Biological Cover
Percent Cover of Live Coral
Concatenation of Major Biological Cover and Percent Major Biological Cover. Used to describe the combination of major biological cover and its percent patchiness of the feature
Specific details of the attributes and values therein can be found in Chapter 1: Benthic Habitat Classification Scheme of "Benthic Habitats of St. John, U.S. Virgin Islands" (Zitello et al. 2009).
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.
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.
Contact NOAA for distribution options (see Distributor).
