HIGH-PRECISION ARRAY ELEMENT LOCALIZATION FOR VERTICAL LINE ARRAYS INTHE ARCTIC-OCEAN

Array element localization (AEL) surveys are often required to accurat ely localize acoustic instruments (transponders or sensors) in the oce an. These are typically based on transmitting or recording acoustic si gnals from or at a set of well-known positions. A significant limiting factor in many AEL surveys is the uncertainty inherent in these ''kno wn'' positions. In this paper, an inversion algorithm is developed whi ch properly treats both transponder anti sensor positions as unknowns. subject to available a priori information in the form of position est imates and uncertainties. The algorithm essentially consists of an ite rative linearized inversion of the raytracing equations employing the method of regularization. The approach is applied to independently loc alize transponders and vertical line array (VLA) sensors that form par t of a three-dimensional sensor array in the Arctic Ocean. Confidence limits estimated via Monte Carlo simulation indicate that transponders and sensors are localized to less than 1 m in three dimensions, The V LA sensor motion, monitored over a seven-week period, appears to be pr edominately driven by tidal cui rents and is consistent with historica l current measurements for the region.