Exploration on deeper water puts high requirements on underwater positioning for both DP operations and survey applications. Acoustic positioning systems are continuously improved to meet new requirements. Development carried out during the last years for the HUGlN AUV has brought new technology available for combining acoustic positioning with inertial navigation. Based on this the HAlN system is developed as an extension to the HiPAP and HPR systems. HAlN Position ReferenceThe HAlN system for vessel positioning is an aided inertial navigations system. The position drift that is inherent in Inertial Navigation Systems is limited by the acoustic position measurements relative to transponder(s) on the seabed. The system can be used both with SSEL or LBL position input. The HAlN provides an improved position of the vessel which both has increased accuracy and higher update rate than the original position from the acoustic measurements. This extends operational water depth and reduced battery consumption. Position output during acoustic dropout will be maintained. HAlN SubseaThe system is also available in a version for ROV positioning for survey applications. In this version the system also is interfaced to a Doppler velocity log and a pressure sensor. The complementary solutionAcoustic and Inertial positioning principles in combination is ideal, since they have complementary qualities. Acoustic positioning is characterised by relatively high and evenly distributed noise and no drift in the position, whilst inertial positioning has very low shortterm noise and relatively large drift in the position over time.The presentation at Oceans'04 will show the HAlN operational methods, benefits and accuracy figures.

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