Bathymetric mapping of coral reefs in the Red Sea (Hurghada-Egypt) using Landsat7 ETM+ data

For monitoring threats posed on coral reefs a bathymetric map is useful as a base to locate vulnerable areas. For mapping shallow features as coral reefs in the Red Sea, conventional echo sounding methods are usually inappropriate due to the draught of the vessels used. Here remote sensing can bring a solution. Different methods have already been developed to map bathymetry using passive remote sensing. In this paper the modified Depth of Penetration mapping method suggested by Green et al. (2000) is implemented on a Landsat7 ETM+ image. This method is mainly based on the different attenuation coefficients of sequencing wavelengths in water. Using additional ground-truth observations, depths can be estimated. Although this method results in an acceptable bathymetric map, some deviations from groundtruth occur. These differences caused by errors inherent to the method used, field sampling or implementation, are examined and possible solutions are presented