A Review of Coral Reef Remote Sensing

Abstract

Global coral reef ecosystems degrade quickly as a result of disturbances from climate change and human activities.Getting knowledge of coral reef benthic cover through remote sensing is of great importance to coral reef management and protection.A significant problem involved with remote sensing of submerged coral reef ecosystems is that water column overlying the substrate significantly affects the remotely sensed signal due to optical attenuation of light in water.Water depth,water quality,tidal variability,surface roughness,spectral similarity of various substrata,as well as spatial heterogeneity,combine to limit the accuracy with which remote sensing can be used to identify coral reef substrate type.In this article,international research work in coral reef remote sensing field were reviewed and five main topics were summarized and expounded,which were separabiltiy analysis of substrate spectral reflectance, water correction methods,spectral unmixing modeling and methods,remote sensing images classification and change detection.Research results acknowledge that classification of benthic covers,especially at fine levels,needs high spectral resolution.When spectral information is not enough,utilizing spatial information can be expected to give improvements.Optical remote sensors usually fail to get coral reef information as a result of their limited ability of water penetration and cloud contamination.Based on the understanding of coral reef remote sensing status,prospects of future development were put forward.They include as follows: hyperspectral data will be used more frequently due to their more accessibility;spatial information,including textural and contextual information,would be attached with greater importance in order to enhance classification and change detection accuracy;much more efforts need to be devoted to improving theoretical physical models of coral reef remote sensing;optical sensors can be combined with acoustic sensors;optical sensors especially to monitor coral reef environments should be designed and launched.