Determination of Static and Time Varying Dipole Source - Sensor Geometry during Sea Trials Using Differential Global Positioning System.

摘要

Global positioning system (GPS) navigational equipment is used in differential mode to determine the time varying geometry of a boat attached to a submerged dipole source and a sensor positioned on the seafloor which is marked by a surface buoy. The requirement is to track the position of the source relative to the sensor on the seabed in sea depths less than 40 metres in the vicinity of Sydney Harbor. A differential GPS (DGPS) system is formed from two or three low cost navigational units, one of which is located at a surveyed reference site and the other is located onboard the vessel. A third unit may be temporarily located at the sea surface above the sensor positioned on the seafloor. The differential system relies on software developed to apply the GPS correction obtained from the reference station to the remote stations after the geographical coordinates have been recorded. Static DGPS measurements using a 7 km baseline between remote and reference datums gave a position accuracy limited by the resolution of the GPS receiver. As a test for kinematic DGPS, the positional accuracy of the moving vessel was checked against the position coordinates derived from the laser tracking facility of the Shark Point Degaussing Range, Sydney Harbour. The agreement was usually found to be better than about 5 m, typically +/- 2 m. DGPS also enabled accurate submarine tracking at periscope depth by interfacing the submarine UHF antenna to the GPS receiver. A discussion of operational issues in the use of DGPS is also included. Navigation, DGPS, GPS.