A diver-operated hyperspectral imaging and topographic surveying system for automated mapping of benthic habitats

Abstract

We developed a novel integrated technology for diver-operated surveying of shallow marine ecosystems. The HyperDiver system captures rich multifaceted data in each transect: hyperspectral and color imagery, topographic profiles, incident irradiance and water chemistry at a rate of 15–30 m2 per minute. From surveys in a coral reef following standard diver protocols, we show how the rich optical detail can be leveraged to generate photopigment abundance and benthic composition maps. We applied machine learning techniques, with a minor annotation effort (<2% of pixels), to automatically generate cm-scale benthic habitat maps of high taxonomic resolution and accuracy (93–97%). The ability to efficiently map benthic composition, photopigment densities and rugosity at reef scales is a compelling contribution to modernize reef monitoring. Seafloor-level hyperspectral images can be used for automated mapping, avoiding operator bias in the analysis and deliver the degree of detail necessary for standardized environmental monitoring. The technique can deliver fast, objective and economic reef survey results, making it a valuable tool for coastal managers and reef ecologists. Underwater hyperspectral surveying shares the vantage point of the high spatial and taxonomic resolution restricted to field surveys, with analytical techniques of remote sensing and provides targeted validation for aerial monitoring.

Water Column Optical Properties of Pacific Coral Reefs Across Geomorphic Zones and in Comparison to Offshore Waters

“…Despite decades of in situ and laboratory-based surveys and experimental study, coral reefs are not fully understood as ecosystems across spatial scales [3,[139][140][141][142]. In addition to satellites and aircraft, using optical techniques from a diversity of platforms including divers [25,143,144], autonomous underwater vehicles [145], ships and kayaks [55], and drones [146] will also help to bridge this gap and unlock new methods to quantify physiology, metabolism, primary production, calcification and other biogeochemical processes. The complex three-dimensional nature of the benthos also influences light absorption [147] and reflectance [148].…”

Monitoring of Coral Reefs Using Artificial Intelligence: A Feasible and Cost-Effective Approach

“…Using multi-scale or regional networks to account for the taxa-specific model sensitivity (e.g., [35]) may help by increasing versatility in the definition of the region of interests and maximising the accuracy of abundance estimations. Furthermore, light spectral signature (e.g., fluorescence, reflection) may offer an alternative to expand the parameters that define phototrophic or pigmented organisms [36,37].…”

An Under-Ice Hyperspectral and RGB Imaging System to Capture Fine-Scale Biophysical Properties of Sea Ice

“…The Ecotone UHI has also been equipped onto unmanned seafloor vehicles (USV) for shallow seafloor mapping [33]. The other two are documented in [32,34] and comprise of stationary time-lapse observations and a diver-operated set-up.…”

“…Low light levels will push sensors to their sensitivity limits, necessarily affect SNR and hinder the integration of pushbroom HI payloads onto more efficient and dynamic underwater platforms, such as ROVs and AUVs. A series of studies have already employed pushbroom HI sensors for seafloor mapping using ROVs [35,36,76], diver operated systems [32], or unmanned surface systems [33]. A first study has also discussed HI feasibility onto AUVs [115].…”

“…Underwater applications of HI are still in a development phase but are presenting opportunities to monitor and map shallow benthic habitats [32,33] and intertidal microphytobenthic environments [34]. HI cameras have also been mounted onto deep-sea ROVs and shown to be a useful taxonomic tool for macrofauna [35] and mapping of manganese nodules [36].…”