Testing a GPS-based System for the Support of Ship Berthing Operations

摘要

This study was conducted concerning a ship's automaticrnberthing system where is required precise and real-timernestimation of the state vector, i.e., for a 300-m ship,rnposition ±0.3 m, velocity ±0.02 m/s, heading ±0.05° andrnyaw rate ±0.02°/s.rnGPS (Global Positioning System) is now fully operationalrnand provides a continuous all-weather service worldwide.rnRapid and reliable cycle ambiguity resolution provides thernultimate accuracy for GPS positioning and attituderndetermination. In the present study, algorithms for a GPS-basedrnsystem, have been developed, which makernsynergetic use of all the GPS observations and therncharacteristics of ship's berthing.rnTests were conducted on board the hydrographic soundingrnship "F.C.G. Smith", to verify the performance ofrnalgorithms and the quality of the navigation solution forrnan onboard GPS-based system consisting of an optimalrn4-antenna configuration (baseline ca. 1.4 m). The ship is arnstable catamaran platform, which was considered suitablernfor simulating a large ship. During the tests, the distancernbetween the ship and the reference station was always lessrnthan 1 km. The position of the ship was compared to thatrnprovided by an automatic tracking total station. Attituderndetermination was tested by comparing GPS results withrnthose of the TSS sensor and gyrocompass onboard.rnThe correct solution of ambiguities allowed preciserndetermination of position and attitude and led to thernfollowing results: 1) the RMS values (1s) of therndifference of horizontal position and height between therntotal station and GPS were ±6 cm in horizontal positionrnand ±2 cm in height, in moving environment for therndistance to the reference station, ca. 1 km and 2) the RMSrnvalues of the difference of GPS attitude angles with thernoutputs of external sensors were: ±0.4° for roll, ±0.3° forrnpitch and ±0.6° for yaw with 1.4 m of antenna separation.rnThe algorithms developed allow fast ambiguity resolutionrnand would be suitable for real-time applications. Since thernprecision of attitude can be improved by extending thernbaselines between the antennas on board the shiprn(ca. 10 m), the GPS-based system has the potential to bernused for a berthing guidance system.