Uncrewed Systems Technology 049 - April/May 2023

99 This boom in the supply of uncrewed marine vehicles has made ocean data more accessible than ever. At the same time, a lot of effort has gone into engineering sonars to provide cleaner, higher-resolution data without relying on excessively large arrays. While data quality can in theory be improved by carrying out more post-processing, the demand for data these days is such that customers can no longer wait for that to be carried out. Enhancing sonars through a better understanding of acoustics, improved transducer and hydrophone designs, and the latest FPGAs and DSPs therefore provides more and better data, and greatly accelerates the speed and efficiency at which the oceans can be studied and modelled. AI in bathymetry Multi-beam echo sounders (MBEs) have grown in popularity compared with sidescan sonars among users of bathymetric surveys. That includes commercial customers building seafloor maps for construction or geophysical analysis, and defence users engaged in mine countermeasures or anti- submarine monitoring. Reasons for this include the ability of MBEs to gather directional information from reflected soundwaves via beamforming, as well as the more complete mapping they provide (typically in a fan shape beneath the vehicle) than sidescan sonars, which in most configurations do not show what is directly beneath the vehicle. Some newer sidescan sonars are designed to compensate for this mechanically, but developing a new sonar typically takes at least 5 years, making it hard for sonar engineers to react to market trends with newly optimised architectures of sonar products. Being typically downward-facing, with no blind spots in acousticmeasurements other than shadows created by objects on the seafloor, MBEs have been able to outpace advances in sidescan sonars to an extent by complementing their architectureswith an array of newAI capabilities powered by advances in computing power and digital signal processing. As mentioned, USVs are being engineered with greater reactivity to their sonar data. One new trend in some sonar designs that is helping to allow this is automated tracking and control via sonar readings, not only of the USV but of the sonar itself. Traditionally, crewed survey vessels would use an online surveyor to track the health and telemetry readings of every payload sensor on board, all of which had to be constantly optimised, be it for power output, coverage, range, frequency or other parameters. However, the optimisations would rarely be based on the sonar (or other sensor data) results obtained, but on look-up tables instead. Given that the quality of real-time data from sonars has improved greatly over the past few years, some developers have recognised that this presents an opportunity for the sonars to control themselves. By examining their own acoustic pulse returns and seeing whether initial results indicate sufficient levels of detail for actionable 3Dmodels for the end-user, the sonar can determine – by itself or using a companion computer on the USV – whether to alter the power it is using for scanning. It can even do so digitally, which means for instance that it could calculate a precise figure for the optimal frequency based on its acoustic returns. For example, it could choose 217 kHz, whereas older analogue control Sonar systems | Focus While data quality can be improved by carrying out more post-processing, the demand for data is such that users can no longer wait for that to be done Uncrewed Systems Technology | April/May 2023 Growing demand for ocean data is driving down the cost and integration barriers for echo sounders on USVs and UUVs (Courtesy of Blueprint Subsea)