Intercomparison of shallow water bathymetry, hydro-optics, and benthos mapping techniques in Australian and Caribbean coastal environments

Science, resource management, and defense need algorithms capable of using airborne or satellite imagery to accu rately map bathymetry, water quality, and substrate composition in optically shallow waters. Although a variety of inver sion algorithms are available, there has been limited assessment of performance and no work has been published com paring their accuracy and efficiency. This paper compares the absolute and relative accuracies and computational effi ciencies of one empirical and five radiative-transfer-based published approaches applied to coastal sites at Lee Stocking Island in the Bahamas and Moreton Bay in eastern Australia. These sites have published airborne hyperspectral data and field data. The assessment showed that (1) radiative-transfer‐based methods were more accurate than the empirical approach for bathymetric retrieval, and the accuracies and processing times were inversely related to the complexity of the models used; (2) all inversion methods provided moder ately accurate retrievals of bathymetry, water column inher ent optical properties, and benthic reflectance in waters less than 13 m deep with homogeneous to heterogeneous benth ic/substrate covers; (3) slightly higher accuracy retrievals were obtained from locally parameterized methods; and (4) no method compared here can be considered optimal for all situ ations. The results provide a guide to the conditions where each approach may be used (available image and field data and processing capability). A re-analysis of these same or addi tional sites with satellite hyperspectral data with lower spatial and radiometric resolution, but higher temporal resolution would be instructive to establish guidelines for repeatable regional to global scale shallow water mapping approaches. Optically shallow waters, those where the bottom is visible from the water surface and measurably influences the waterleaving radiance, include inland waters through to estuarine and tropical coral reef and temperate coastal ecosystems. Over