Improving Acoustic Range-Only Localisation by Selection of Transmission Time

This work looks at when to transmit localisation messages in the scenario where an Autonomous Surface Vehicle (ASV) has a planned path and can estimate a submerged AUV's positions based on acoustic updates. Acoustic localisation messages are in general transmitted periodically, but by estimating the movement of the involved vehicles, messages can be transmitted at a time when the geometrical relationship between vehicles should reduce the receiving vehicles error and uncertainty to the greatest extent. This paper looks at how selection of Time of Launch (ToL) within a Time-Division Multiple Access slot can reduce this based on history of transmission and the estimated geometrical relationship between vehicles over time. The method to select ToL is dependent on the localisation method, we look at this from the perspective of Extended Kalman Filter and to solve the trilateration problem using Non-linear Least Squares. The benefit of proposed approach is in scenarios where the operating vehicles have their own objectives, and cannot adapt their path to achieve a more beneficial transmission position. The proposed approach shows a reduction of error and uncertainty, while using a navigational dataset collected by an Autonomous Underwater Vehicle when compared to other methods of which transmission times are selected.