Data Management Plan

The National Oceanic and Atmospheric Administration's (NOAA) National Ocean Service (NOS) is tasked with the coral mapping element of the U.S. Coral Reef Task Force (CRTF) under the authority of Executive Order 13089. NOS is responsible for coral reef mapping in Puerto Rico, the U.S. Virgin Islands, the Northwest Hawaiian Islands, the Main Eight Hawaiian Islands, and the U.S. Territories and Freely Associated States of the Pacific. Space Imaging, Inc (SI) and Analytical Laboratories of Hawaii, LLC (ALH) has produced GIS-compatible benthic habitat digital maps of the Republic of Palau using the classification scheme defined by NOAA. The map products produced through this project include baseline data of U.S. coral reefs, location of coral reef boundaries and overall coral reef cover, and the geomorphologic structure in and around coral reef systems. Maps include the 9 major and 23 detailed biological cover types, 4 major and 14 detailed geomorphological structure types, and 15 mutually exclusive zones specified in NOAA's hierarchical classification manual for coastal waters of the Republic of Palau. Benthic habitats are delineated from the coastline to water depths of 30 meters in GIS using manual interpretation techniques. NOAA utilizes IKONOS Multispectral (MSI) Satellite Imagery from Space Imaging, Inc., consisting of both newly acquired and archived imagery. The imagery consists of 1m panchromatic and 4m MSI with a horizontal accuracy of at least 5m CE95 at 1:4,800 National Map Accuracy Standard (NMAS). Once the imagery is processed, NOAA will use ALH's hand-digitize GIS approach to produce the benthic habitat maps at a minimum mapping unit of one acre, as well as NOAA's preferred random stratified accuracy assessment method.

Process Steps:

• 2007-01-01 00:00:00 - All of the IKONOS imagery was purchased in National Imagery Transmission Format (NITF) with the associated Rational Polynomial Coefficients (RPCs or satellite ephemeris data). Raw satellite images were converted from Digital Numbers (DNs) to normalized reflectance. As part of the conversion from DNs to at-satellite reflectance, the following equation is used (Green et al. 2000):R = pi * L/ (Eo cos(theta0) 1/r2)L = radiance (from calibration provided by Space Imaging). r = earth-sun distance in Astronomical Units. theta0 = the solar zenith angle. Eo = the mean solar exo-atmospheric irradiance in each band. (A convolution of the spectral response and solar radiation from Neckel and Labs (1984) was used to get Eo.) The acquisition angles (ephemeris data) of the satellite relative to the ground at the time of image acquisition were also used. Calibration coefficients for the satellite, provided by Space Imaging, were used to calculate at-satellite radiance, which was then transformed to reflectance. The normalized reflectance imagery was then transformed into water reflectance (or the signal less than 10 cm above the water surface). Water reflectance uses the near-infrared band to remove radiance attributed to atmospheric and surface effects (Stumpf et al. 2003). Water reflectance estimates how the signal (photons) received by the satellite is diminished as it passes through the atmosphere on the way down to the water-atmosphere boundary and on the way back up to the satellite after the signal leaves the water-atmosphere boundary. Water reflectance also estimates how the signal at the satellite is diminished by water vapor, clouds, specular effects at the water surface (wave surface glint), and other signal- absorbing and diffusing materials.Georeferencing/mosaicking of the imagery was performed using PCI OrthoEngine module. The NITF IKONOS imagery was orthorectified using the Rational Functions extracted from the NITF, then further supplemented with ground control collected via survey grade GPS and corrected for terrain displacement using the DEM's where available. When multiple scenes were available for a given area, these were collectively incorporated into the orthomosaic project through bundle adjustment. Each scene was exported as a separate orthorectified file for further image processing. In addition, the best segments of each scene were selected for creation of the final mosaic. Segments of each scene were selected to minimize sun glint, cloud interference, turbidity, etc. 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. However, in some cases, clouds, sun glint, or turbid areas could not be replaced with overlapping imagery. In these areas, such obstructions were minimized but could not be eliminated completely.