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

TLDR

Accurate mapping of bathymetry, water quality, and substrate in optically shallow waters is essential for science, resource management, and defense, yet performance of available inversion algorithms has rarely been assessed or compared. This study compares the absolute and relative accuracies and computational efficiencies of one empirical and five radiative‑transfer‑based bathymetric retrieval approaches. The comparison was conducted on Lee Stocking Island in the Bahamas and Moreton Bay in eastern Australia using published airborne hyperspectral data and field measurements. Radiative‑transfer–based methods outperformed the empirical approach for bathymetry, with accuracy and processing time inversely related to model complexity; all methods yielded moderately accurate bathymetry, water‑column optical properties, and benthic reflectance in waters <13 m, with locally parameterized models slightly better, yet no single method is optimal for all conditions, offering a guide to selecting approaches based on data availability and processing capability.

Abstract

Science, resource management, and defense need algorithms capable of using airborne or satellite imagery to accurately map bathymetry, water quality, and substrate composition in optically shallow waters. Although a variety of inversion algorithms are available, there has been limited assessment of performance and no work has been published comparing their accuracy and efficiency. This paper compares the absolute and relative accuracies and computational efficiencies 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 moderately accurate retrievals of bathymetry, water column inherent optical properties, and benthic reflectance in waters less than 13 m deep with homogeneous to heterogeneous benthic/ 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 situations. 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 additional 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.