Bathymetry of near-shore zones in Rongelap Atoll, Marshall Islands using satellite imagery

Large-scale mapping of remote coral reefs requires a sensor that offers imagery with the spatial, spectral, and radiometric resolution suitable for processing large datasets of shoreline and near-shore regions. This study tests the viability of ASTER imagery in deriving accurate bathymetry of nearshore zones in Rongelap, an atoll in the Marshall Islands. A depth estimation algorithm was developed by calculating the ratio between two bands of reflectance data from the ASTER image and estimates depth of the near-shore zones based on the ratio. A dataset of geopositioned in situ measurements using RTK-GPS was obtained with sonar and sounding lines to a depth of 30m. The depth estimates were then compared to the in situ depth readings as a basis for determining accuracy and sensitivity of the ASTER-based ratio algorithm. The results from the ASTER-based ratio algorithm indicate the importance of using blue band reflectance data in satellite-based bathymetric modelling