Modified Short Baseline Acoustic Relative Localization System

Underwater localization is a key element in most underwater communication applications. Since GPS signals highly attenuate in water, precise ranging based techniques for localization need to be developed. In this paper we describe a modified Short Baseline (SBL) acoustic localization system, in which a scheme of multi-channel data acquisition based on LabVIEW, the Generalized Cross Correlation (GCC) algorithm, and the hyperbolic positioning algorithm are used. Simulation results show that the modified SBL acoustic localization system that we proposed can adapt to the underwater harsh environment better, and also can reduce the position statistical error of underwater target significantly.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—We present a new acoustic telemetry method for efficiently estimating positions of tagged marine and freshwater animals using vessel-based active tracking. Vessel-based tracking can require considerable time and effort, which limits both study area size and the number of tagged animals possible for telemetry studies. However, the recently-developed SYNAPS (Synthetic Aperture Positioning System) tracking method allows efficient collection of fine-scale movement information for many tagged animals within large study areas, and therefore enables large surveys to be conducted in a methodical and cost-effective manner. SYNAPS computes position estimates of tagged animals by means of hyperbolic positioning using the geographic location of a mobile hydrophone synchronized with signal detections to create a synthetic hydrophone array. Here we describe the process of tracking with SYNAPS, quantify accuracy and precision of position estimations, and provide guidelines for tracking procedures. SYNAPS position estimates were compared with known positions of fixed tags in both marine (Alaska, USA) and freshwater lake (Ontario, Canada) systems. Accuracy of position estimates ranged from 1.2 m using hull-mounted hydrophones and survey-quality GPS equipment to 23.4 m using towed hydrophones and a navigation-grade GPS receiver. This new tool will facilitate spatially explicit management applications such as aquatic protected area design and essential fish habitat designation by increasing the ability of acoustic telemetry to characterize movement of marine animals at different scales.