Instructions
The first of the three images above is a scaled-down version of the most recent global composite of SeaWiFS one-kilometer data that have been passed through a depth-classification algorithm. The second image shows coral reef locations in red. This image was created by the World Conservation Monitoring Centre using data from a variety of navigational charts and other maps, and is available online through the Reefbase Interactive Map Server, or in the published World Atlas of Coral Reefs (Spalding et al. 2001). The third image shows the locations of images from a variety of sensors which can be viewed with this interface.
Click on any of the three images above to view the full-resolution SeaWiFS bathymetry data for the location clicked upon. You can remove any of the images above by clicking on the appropriate buttons.
SeaWiFS Bathymetry Description
Characterizing water depth in tropical oceans is an important first step for improving the identification and characterization of coral reefs. NOAA scientists have developed a new bathymetry algorithm, originally applied to 4-meter IKONOS imagery (Stumpf et al. 2003b), that could be applied to other instruments with blue and green bands. The algorithm was used to produce a global composite 1-km bathymetry map from using SeaWiFS data (Robinson et al. 2000, Stumpf et al. 1999, 2003a).
The value of each pixel in the full-resolution SeaWiFS depth classification image is derived from depths computed from different SeaWiFS overflights so that cloud pixels can be removed and best depth estimates developed that eliminate transient effects of sediment, chlorophyll, etc. We have used the median measurement (after cloud pixels have been removed) to represent each 0.01 by 0.01 degree location on the map.
The most current SeaWiFS-derived depth map was updated on 6 November 2002 and represents the contribution of 28,937 GAC resolution files (all five years of the SeaWiFS mission), 25,682 recorded LAC-resolution files and 1,804 HRPT station files from all around the world. The image below shows how many separate SeaWiFS pixels (including cloudy pixels) were used to determine each pixel on the final map. As of 13 November 2002, no map pixel had fewer than 4 input pixels, and many had more than 200.
The source data for the bathymetric images displayed at this website are available here.
The global SeaWiFS bathymetry map has been used to identify and correct errors in the UNEP-WCMC Reef Map. Combining the SeaWiFS bathymetry product with the WCMC map has increased map accuracy for use in evaluating the global distribution of marine protected areas (Green et al. in review).
Data Archive Proof-of-Concept
This web interface was also developed as a proof of concept for the use of remotely sensed earth observations from various platforms in the mapping of coral reefs around the globe. A NASA-sponsored partnership between remote sensing scientists, international agencies and NGOs has developed from this prototype, and a full Landsat Coral Reef Data Archive is now available.
Other data sets displayed by this interface include:
AVIRIS Hyperspectral data collection was conducted with a NASA high altitude aircraft over the Hawaiian islands in April 2000. Preliminary data processing has been completed at NASA's Jet Propulsion Laboratory and tapes containing 104 flight lines are being sent to NASA/Goddard Space Flight Center for further processing and distribution.
This work is a joint project of:
References:
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