Benthic Habitats of Guam Derived From IKONOS Imagery, 2001-2003

This project is a cooperative effort among the National Ocean Service, National Centers for Coastal Ocean Science, Center for Coastal Monitoring and Assessment; the University of Hawaii; BAE Systems Spectral Solutions; and Analytical Laboratories of Hawaii, LLC. The goal of the work was to map the coral reef habitats of American Samoa, Guam and the Commonwealth of the Northern Mariana Islands by visual interpretation and manual delineation of IKONOS satellite imagery. A two tiered habitat classification system was tested and implemented in this work. It integrates geomorphologic reef structure and biological cover into a single scheme and subsets each into detail. It also includes thirteen zones. Benthic features were mapped that covered an area of 104 square kilometers of which 32.9 were unconsolidated sediment and 71.6 were coral reef and hard bottom. Of the coral reef and hard bottom class, 35.6% is colonized by greater than 10% coral cover.

The National Ocean Service is conducting a map production effort 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 National Oceanic and Atmospheric Administration (NOAA) National Centers for Coastal Ocean Science (NCCOS) produced this data CD-ROM. NCCOS Biogeography Branch does not guarantee the accuracy of the geographic features or attributes. Please see the metadata records for each data set for complete information on the source, limitations, and proper use.

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Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 1; ESRI ArcCatalog 9.0.0.535

A statistically robust field data set was collected to assess the thematic accuracy of the map products. A random stratified sampling method was implemented to select field sites to conduct this test. Each site was navigated to using a Trimble Geo Explorer 3 GPS data logger, and positional data was acquired. A total of 1,113 GPS waypoints were occupied and benthic characterizations conducted for the purpose of accuracy assessment. Areas that were obscured by cloud cover or where other environmental conditions such as glint of turbidity prevented visual interpretation of the benthic habitats were assigned an attribute of "unknown". Field observations that fell in polygons designated "unknown" were not included in the statistical analysis. During this survey, 5 of the 1,113 field observations were excluded for this reason and 1,108 observations were used in the accuracy assessment.A statistical analysis that generated a Tau statistic was preformed. The Tau statistic for the major classes exceeded 0.85 and for detailed classes exceeded 0.75. Overall thematic accuracy was established as 98.7% and 92.6% for the major structure and cover classes and 87.8% and 80.9% for the detailed classes respectively for the entire Mariana Archipelago.

RMS from digitized output was determined using the ESRI RMEer2 extension and shown to be less than 1m when conducted at 1:6000 scale.

NOAA supplied georeferenced imagery to Analytical Laboratories of Hawaii through BAE Systems Spectral Solutions. Delineation of all habitat boundaries was conducted with the image scale at 1:6,000. This ensures that the level of detail produced by the photo interpreter is uniform throughout the project. Also, NOAA has shown from similar mapping efforts in the Caribbean and Florida Keys, that little additional information is gained from having the image at a smaller scale and the labor intensity increased significantly. The minimum mapping unit (MMU) for identifying habitats or features was 1 acre. The software utilized in this project was designed to alert the photo interpreter each time a polygon was drawn smaller than the MMU. When this occurred the photo interpreter has the choice whether to include the polygon in the data set. Only in areas where local coral reef managers expressed interest in specific map classes or in Marine Protected Areas were polygons of smaller then the MMU allowed.

All mapping was conducted from orthorectified IKONOS satellite imagery provided by NOS prior to map production. IKONOS satellite imagery was corrected for atmospheric and water column effects, color balanced, pan sharpened and deglinted. During the digitizing process, image stretches and manipulating image contrast, brightness and color balance were performed in the ArcView Image Analysis Extension to enhance features in the processed imagery. GIS topologic quality was established by executing ArcView 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.