Impact of Natural Gas Seeps on the Navigation of an Autonomous Underwater Vehicle

Abstract

Oceans preservation and protection have become increasingly relevant topics to tackle climate change. To this end, Autonomous Underwater Vehicles (AUVs) provide a useful means to carry out inspection and monitoring operations in full autonomy. A particular scenario in which AUVs are crucial involves the detection and mapping of underwater gas leaks, whether these are due to damaged offshore structures or naturally released from the seafloor. In this context, the proposed work investigates the effects of gas seeps on the navigation performance of AUVs. Indeed, the navigation of underwater vehicles mostly relies on acoustic sensors, as Doppler Velocity Log (DVL), which can be negatively affected by the presence of gas bubbles. The paper explores two solutions, based on two different acoustic sensors working at distinct frequencies: a DVL sensor and an Ultra-Short BaseLine (USBL) device. Both strategies have been implemented and tested during at-sea experiments, where gas leaks have been artificially reproduced. Results showed that both methods suffer from the presence of gas bubbles, causing erroneous DVL measurements and lost of USBL connectivity, respectively.