Ground Truth Data Used to Map the Benthic Habitat of the U.S. Virgin Islands

This project is a cooperative effort among the National Ocean Service, National Centers for Coastal Ocean Science, Center for Coastal Monitoring and Assessment; U.S. Geological Survey; National Park Service; and the National Geophysical Data Center to produce benthic habitat maps and georeferenced imagery for Puerto Rico and the U.S. Virgin Islands. This project was conducted in support of the U.S. Coral Reef Task Force. These point data were generated while conducting ground validation during map preparation.

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.

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The Ground Truth Points are available in a spreadsheet format.

tab delimited text files; UTM Zone 19 coordinates; habitat type; dominant benthic elements are listed

Benthic features were assigned one of twenty-six habitat types ranging from sand to coral. A complete description of these classification categories can be found at http://ccma.nos.noaa.gov/products/biogeography/benthic/htm/manual.aspx

Data are not to be used for navigation.

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Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 3; ESRI ArcCatalog 8.3.0.800

Habitat type(s), zone, approximate depth, position (GPS), image number, and other descriptive information were recorded at each site. Field data for each site was then compiled into a text table with a latitude/longitude field to allow overlay of the field information on the mosaic and habitat polygons. Once data were entered into spreadsheet format a careful review was conducted to ensure that all labels were complete and accurate.

Spatial data meets or exceeds national map accuracy standards for fixed features.

Depth values are reported in feet from water surface. Values should be considered estimates only. In some cases, no estimate of depth could be provided.

Following processing of the field data, polygon boundaries and habitat classifications were created or revised where necessary, and zone attributes were assigned to each polygon using the Habitat Digitizer Extension. This draft of the habitat maps was then reviewed and revised with the guidance of a panel of local experts at peer review sessions in Puerto Rico, the U.S. Virgin Islands, and over the Internet. Review session participants included members of the local research and management community. During these peer review sessions, particular attention was given to polygons labeled as "unknown" and areas not visited during ground truth activities. Revisions based on comments from local experts were then completed and final habitat maps were produced.

Diapositives, and when available, draft delineations were used in the field to facilitate comparison of signatures in the imagery to actual habitats at each site. Individual sites were visually evaluated by snorkeling and free diving or directly from the boat in shallow, clear water. Where depth and water clarity permitted, the diapositives were used to navigate across multiple bottom features allowing continuous confirmation of habitat types and transitions between each site.