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CENSSIS SEABED : DIVERSE APPROACHES FOR IMAGING SHALLOW AND DEEP CORAL REEFS

The main task of the Center for Subsurface Sensing and Imaging Systems (CenSSIS), funded by the National Science Foundation, is to develop appropriate techniques to separate complex subsurface signals. This multi-university Engineering Research Center aims to revolutionize the existing technology for detecting and imaging objects under different layers, including underwater. The University of Puerto Rico at Mayaguez (UPRM), a main partner of CenSSIS, has created SeaBED for the development of improved remote sensing techniques for monitoring coral reefs. SeaBED includes both controlled laboratory facilities and a field test environment in the southwest coast of Puerto Rico that is being used to validate sensors, improve algorithms, understand physical models, and develop extraction tools and classification methods for underwater sensing. Multiple sensors with different spatial and spectral resolutions, such as Landsat TM, IKONOS, Hyperion, and AVIRIS, have been tested. In terms of image processing, different pattern recognition algorithms (e.g., image classification and spectral unmixing) and time series analyses for change detection have been used. Bottom reflectance and remote sensing reflectance have been measured from several coral reef zones, different species, and coral health conditions with a submersible spectroradiometer. Furthermore, for optical imaging of coral reefs present below one attenuation depth (approximately 20 m in oligotrophic waters), which defines a practical limit for effective airborne and satellite remote sensing, we have used an autonomous underwater vehicle (AUV) as an in situ platform for acquiring measurements. High-resolution optical imaging from the AUV is used for mapping and characterizing deeper reefs present between 30 to 100 meters.