The new generation of Electronic Click Detector (ECD): the development and field trials data

The use of envelope detection methods to reduce the bandwidth of an echolocation click into the audio-band is not a new concept. However, the increasing popularity of portable digital recorders with excellent signal to noise performance needs such signal processing if ultrasonic transient data needs to be captured. Similarly, this approach allows high frequency information to be recorded onto video recorder sound tracks providing the advantage of synchronised sound with images for behavioural studies. This paper describes the development of a new generation of ECD with improved performance and includes cetacean echolocation data recorded using this equipment in two independent studies

Underwater position-fixing using digital acoustic communication techniques

SIGLEAvailable from British Library Document Supply Centre- DSC:DXN063599 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Custom-Technology Single-Photon Avalanche Diode Linear Detector Array for Underwater Depth Imaging

We present an optical depth imaging system suitable for highly scattering underwater environments. The system used the time-correlated single-photon counting (TCSPC) technique and the time-of-flight approach to obtain depth profiles. The single-photon detection was provided by a linear array of single-photon avalanche diode (SPAD) detectors fabricated in a customized silicon fabrication technology for optimized efficiency, dark count rate, and jitter performance. The bi-static transceiver comprised a pulsed laser diode source with central wavelength 670 nm, a linear array of 16 × 1 Si-SPAD detectors, with a dedicated TCSPC acquisition module. Cylindrical lenses were used to collect the light scattered by the target and image it onto the sensor. These laboratory-based experiments demonstrated single-photon depth imaging at a range of 1.65 m in highly scattering conditions, equivalent up to 8.3 attenuation lengths between the system and the target, using average optical powers of up to 15 mW. The depth and spatial resolution of this sensor were investigated in different scattering conditions

Autonomous Identification of Suitable Geotechnical Measurement Locations using Underwater Vehicles

Determining the geotechnical seafloor properties needed to plan subsea infrastructure is time consuming and expensive as it requires soil sampling or in-situ contact measurements to be made using Remotely Operated Vehicles or ship based systems. To increase the efficiency of such surveys, we introduce a predictive framework for autonomous underwater vehicles (AUV) to determine locations where they can land and make contact measurements. We introduce a geotechnical measurability index that is computed using high, cm-resolution AUV observations. To address the small footprint of high-resolution AUV observations, our method infers the distribution of measurability onto more widely available remote sensed bathymetry that has resolutions of tens of centimeters to metres. Features are extracted from these low-resolution priors using an unsupervised Location-Guided Autoencoder. Geotechnical measurability maps are generated using a Bayesian Neural Network that combines these features with the geotechnical measurability calculated from high-resolution AUV observations to infer the measurability over a wide area. The framework is demonstrated using AUV structured light mapping data that was obtained from a $420\times 120m$ region of the Takuyo Daigo seamount. The data was artificially down sampled to simulate low resolution priors with sub-regions observed at high-resolution. The geotechnical measurability maps generated using the predictive framework preserve details that would otherwise be lost if the measurability index was calculated directly based on low resolution priors. </p

High-resolution visual seafloor mapping and classification using long range capable AUV for ship-free benthic surveys

BioCam is a 4000 m depth rated high-resolution mapping instrument that uses lasers, strobes and cameras to generate multi-hectare 3D reconstructions of the seafloor at sub-centimetre resolution. These can be used to analyse seafloor ecology as well as the fine-scale features of seafloor terrains. BioCam was first deployed with the autonomous underwater vehicle (AUV) Autosub Long Range (ALR), also known as "Boaty McBoatface", in July 2022 using the research vessel RRS Discovery. During several dives a total of 80 ha of seafloor in the Greater Haig Fras and the South West Deeps (East) Marine Conservation Zones (MCZ) were visually mapped from altitudes between 4 and 5.5 m and sub-centimetre resolution bathymetry maps were generated. During the cruise, the AUV and BioCam were left onsite while the ship travelled to a new location, and both systems were controlled via satellite communication to upload new missions and confirm data quality, demonstrating the over-the-horizon operation capability needed to enable future ship-free deployments

High-resolution visual seafloor mapping and classification using long range capable AUV for ship-free benthic surveys

BioCam is a 4000m depth rated high-resolution mapping instrument that uses lasers, strobes and cameras to generate multi-hectare 3D reconstructions of the seafloor at sub-centimetre resolution. These can be used to analyse seafloor ecology as well as the fine-scale features of seafloor terrains. BioCam was first deployed with the autonomous underwater vehicle (AUV) Autosub Long Range (ALR), also known as “Boaty McBoatface”, in July 2022 using the research vessel RRS Discovery. During several dives a total of 80ha of seafloor in the Greater Haig Fras and the South West Deeps (East) Marine Conservation Zones (MCZ) were visually mapped from altitudes between 4 and 5.5 m and sub-centimetre resolution bathymetry maps were generated. During the cruise, the AUV and BioCam were left onsite while the ship travelled to a new location, and both systems were controlled via satellite communication to upload new missions and confirm data quality, demonstrating the over-the-horizon operation capability needed to enable future ship-free deployments