Precision Subsea Navigation System

Abstract

A precision acoustic navigation system based upon the short-baseline method of position measurement provides a complete local navigation system for deep-ocean search and survey operations involving a surface vessel and a submersible. A unique use of a single beacon/transponder on the ocean floor and a similar unit on the submersible allows the system to accurately measure and display the relative positions between the reference beacon, the submersible, and the surface vessel. The specific equipment is the Honeywell RS-505/DE Acoustic Position Indicator with Precision Navigation Processor. The “DE” version of the standard RS-505 short-baseline system is a Deep-operating, Extended-range model. The Precision Navigation Processor consists of a digital data processor, which is used to enhance accuracy by reducing instrumentation errors and by providing compensation for the environment (sound-speed variations, ray bending, etc.). The system uses two independent sets of processors to simultaneously measure both the position of the subsea vehicle and the reference point. The position of the subsea vehicle relative to the reference point is obtained by a differential position-measurement technique. Typical accuracy performance of this system is 0.2 to 1 percent of range. The highest accuracy occurs when the reference point and submersible are within a 90-degree cone below the surface support vessel. The normal operating range is 12 times the water depth. The operating range may be extended by using additional bottom units.