Evaluation of RTK-OTF Positioning System for Free Running Manoeuvrability Test of a Model Ship

Abstract

Free running model test using Real-Time-Kinematic On-The Fly (RTK-OTF) mode in GPS was carried out at 80-by-80 meter square ship model basin. The measuring system consists of three GPS receivers, one radio link and an onboard personal computer for data storage. One GPS receiver was located on the shore as a base station which transmits reference data every 1.0 second and two others were on the model ship as mobile stations which produced fore and aft positions data every 0.2 second (5Hz) or 1.0 second (1Hz) selectively. Ultrasonic Positioning System (UPS) was also used for comparison to discuss accuracy and reliability of GPS data. It is concluded that GPS, even in 5Hz fast sampling if it is used in RTK-OTF mode, has sufficient accuracy for positioning and analyzing manoeuvring motion of a free running model ship in calm water and can be a reliable tool not only because of its accuracy but also the property that it is portable, does not require calibration and does not disturb flow around model ships.