A high precision calibration method for long baseline acoustic positioning systems

This paper gives the theory and formulas to show that high precision calibration for underwater beacon arrays in long baseline (LBL) is the basement of high precision target tracking. The traditional method calibrates beacon separately using trilateration which is highly affected by survey trajectory and sound velocity profile. The performance is undesirable with bad precision and low efficiency. To solve this problem, this paper proposes a calibration method for relative calibration using the distances measured between undersea beacons and depths of each beacons to form observation equations. The positions of beacons are calibrated relatively by the distances and the depth measurements. The precision of calibrated beacons is equal to the precision of distance measurements with high efficiency and low complexity for operation. The analysis and experimental results show this method has better precision of calibration than traditional method, the horizontal precision is determined by the precision of distance measurement which is less than decimal meter and the depth precision is determined by the precision of pressure sensor. This method also reduces the calibration time efficiently. Compared with traditional method, this method can reduce the calibration time nearly 10 times, especially in deep sea and large scale operation. This paper also analyses the different performance in tracking target between traditional method and the method we proposed, the effect of sound velocity profile and beacon array topology. This method can be widely used for LBL acoustic positioning systems, which has great value in ocean engineering.