HAIN – Hydroacoustic Aided Inertial Navigation

An Inertial Measurement Unit (IMU) measures its own movement. This IMU is the core component in an Inertial Navigation System (INS) which processes data from the IMU sensor in a computer. The position measurements from an INS are very accurate over a short time frame, but the position data will drift more and more over time. The IMU is therefore not suitable as a DP reference sensor on its own, but it is one out of two main components in a HAIN Reference system.

The IMU data is processed together with position data from an underwater Hydroacoustic Position Reference system in a computer that then will output the unique combined data characterized in HAIN. The vessel position, velocity, heading and attitude are updated at 300 Hz, based on the readings from the IMU, and corrected every time a new acoustic position is measured.

HAIN Reference can therefore be seen as an add-on to the acoustic reference system. It improves the robustness, quality and reliability of the acoustic reference system dramatically and gives you the best and most reliable acoustic reference system available.

HAIN Reference system has the following main advantages:
• It maintains the High update rate (1 second) output to the DP regardless of water depth
• It filters out the acoustic position noise
• It will provide the DP with position data even minutes after loosing the acoustic signals

The deeper water, the more valuable is the HAIN Reference investment. However, experiences from drilling rigs have even in shallow waters also shown great value in position stability. The user will be able to work longer in heavy weather and to have a more dependable reference system.