1 Terrain Referenced Navigation of AUVs and Submarines Using Multibeam Echo Sounders

Most AUV and submarine navigation systems are based on accurate low drift inertial navigation systems (INS) designed to sustain submerged operation for long periods of time. Regardless of velocity aiding sensor and INS quality, the position accu-racy will eventually decrease necessitating position updates. When GPS surface fixes are not allowed due to vulnerability, covertness or efficiency, terrain referenced bathymetric naviga-tion is a well-suited method for submerged position updates. In principle terrain navigation runs on any sensor providing bathymetric data. The paper focuses on use of multibeam echo sounder (MBE), which is particularly attractive because of its wide coverage. MBEs are also ideal sensors for terrain mapping. In rapid environmental assessment (REA) and intelligence, surveillance, target acquisition and reconnaissance (ISTAR) scenarios, bathymetric mapping is an important capability. MBEs typically come with software for in-situ chart production and seabed classification. A FFI developed terrain navigation system is integrated with the inertial navigation system on the HUGIN AUV. A Norwegian submarine is equipped with a multibeam echo sounder in an experimental set-up.