17 / 2023-07-24 10:52:34

An intercomparison of remote sensing approaches for bathymetry, water’s optical properties and benthic types of optically shallow waters based on a co-registered database

Shallow water,,Bathymetry,,Inherent optical properties

 Shallow water (SW) is an important region of the marine ecosystem and carbon fixation which need to be adequately monitored, where inversion of radiometric measurements, or remote sensing (RS), is a cost-effective way for the observation of large areas. A number of approaches or algorithms have been developed to map bathymetry, water quality, and substrate composition from RS. However, there is a lack of guidance on which method is most suitable or accurate for various situations encountered, which is always hindered by the lack of comprehensive, high fidelity, data, in particular to the high heterogeneous shallow environments. In the past years, field measurements were carried out in five representative SW environments around the world, which covered depths in a range of 1-20 m, while bottom substrates varied from sand to seagrass and to various types of coral, so a unique and comprehensive SW database has been compiled. More importantly, these measurements were obtained concurrently and co-registered, thus no differences in data location for each set of bottom depth, picture of sea bottom, and remote sensing reflectance (R_rs). With this database, we compared the performance of a few typical algorithms for shallow water RS. The assessment showed that 1) The error in depth inversion is 10% higher for bottoms with biologically active substrates than that of non-biological substrate. 2) For bottoms mixed substrates, it is important to model the combination of the different contributions to bottom reflectance from each substrate. These results provide use guidance on further improving remote sensing algorithms for SW environments.