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

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.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

A semianalytical ocean color inversion algorithm with explicit water column depth and substrate reflectance parameterization

“…[2009]; BRUCE- Klonowski et al [2007]; SAMBUCA- Wettle and Brando [2006]) and CRISTAL have shown particular merit when applied to hyperspectral imagery (contiguous spectral bands, resolution $5 nm) Dekker et al, 2011;Fearns et al, 2011;Garcia et al, 2014a;Goodman and Ustin, 2007;Hedley et al, 2009;Klonowski et al, 2007;Lee et al, 1999;Lesser and Mobley, 2007]. However, these previous studies were designed primarily to demonstrate bathymetric retrieval and benthic classification capabilities for shallow waters, typically less than 10 m depth, with little emphasis on the derived IOP values and downstream geophysical products such as CHL, SPM, and water clarity measures.…”

Environmental and Sensor Limitations in Optical Remote Sensing of Coral Reefs: Implications for Monitoring and Sensor Design

“…The recent trend in analysis algorithms for shallow water benthic remote sensing is to seek a pixel-by-pixel best fit for reflectance from a forward-based radiative transfer model parameterised on benthic reflectance, depth, water optical properties [12,[14][15][16][17][18][19][20][21]. Such algorithms offer the promise of simultaneous derivation of depth, water optical properties and benthic class.…”

Multiple Stable States and Catastrophic Shifts in Coastal Wetlands: Progress, Challenges, and Opportunities in Validating Theory Using Remote Sensing and Other Methods

“…Many studies have used remote sensing to map seagrass meadows around the world [243][244][245][246][247][248][249][250][251]. Several recent studies also focused on the spatial and temporal variability of seagrasses [252][253][254][255][256][257][258][259].…”