Performance analysis of a shipborne gyrocompass with a multi-antenna GPS system

A four-receiver configuration was used to estimate the three attitude parameters and assess the headings obtained with a Sperry Mark 3 Model C gyrocompass mounted on a 1500 tonnes, 72-m vessel. The GPS configuration consisted of four 10-channel NovAtel GPSCards operating in independent mode. The antenna separations varied between 5 and 15 m. The antenna locations in the ship coordinate system were obtained through a combination of a conventional and GPS survey. The remaining misalignment between the gyrocompass and the multi-receiver configuration was estimated by comparing GPS and gyrocompass heading measurements made throughout the sea trial. The formulation used to estimate the above attitude parameters is described. The multi-receiver data was processed with The University of Calgary´s MULTINAV attitude software. The performance of the gyrocompass was assessed using 10 hours of data collected over a two-day period in Spring 1993 under a wide range of ship manoeuvres such as acceleration, deceleration and 360° turns. The estimated double difference carrier phase residuals, which provide a measure of receiver carrier phase noise and multipath, were below the 5 mm level. The estimated accuracy of the GPS-derived heading parameter was 2.2 arcmins or 0.04° and the standard deviation of the differences between GPS and gyrocompass headings during straight trajectory segments was 0.16°. The use of a two-receiver configuration to determine the heading component was shown to deliver a level of accuracy similar to that obtained with the four-receiver configuration