Underwater transponder positioning and navigation of autonomous underwater vehicles

Navigation of underwater vehicles has been and remains a substantial challenge to all platforms. The need for improved accuracy and robustness, sustainability, and de-risking develops with the emergence of new applications, and with the growing acceptance of autonomous underwater vehicles (AUVs) in both military and civilian institutions. One of the main driving factors is the ability to carry out long-duration missions fully autonomous and without supervision from a surface ship. Combined with inertial navigation, the use of one or several transponders on the seabed is an accurate and cost-effective approach toward solving several of these challenges. The principle discussed in this paper is called underwater transponder positioning (UTP), and requires only one transponder due to tight coupling with the inertial navigation system (INS). For many scenarios UTP may be a better alternative than using a long baseline (LBL) system. This paper reports in-situ and post-processed navigation results obtained with a state-of-the-art UTP aided INS, onboard a HUGIN 1000 AUV. The results demonstrate the feasibility of UTP in large-scale autonomous operations. Excellent realtime navigation is achieved, and the accuracy obtained in postprocessing is shown to be close to that obtained when aiding the INS with an ultra-short baseline (USBL) positioning system.