With the availability of high-accuracy, differential GPS results in real-time, there is a new opportunity to use GPS to accurately measure a vessel's settlement, squat, trim, roll, pitch, and heading. NGS and CS propose to transfer this technology to the Port Authority of Oakland, California. The overall goal of this project is to provide the position of a vessel's keel to within 10 centimeters (about 4 inches) relative to the bottom of the shipping channel.
In support of the project, on December 3-4, 1996, CS, NGS, Trimble Navigation Ltd., and USCG performed GPS tests on a USCG buoy-tender ship. GPS data were used to compute the vessel's squat (dynamic draft), trim, roll, pitch, and heading. During the test, five receivers continually collected data; one at a base station on the USCG pier on Yerba Buena Island and four on the ship, two on the stern and two on the bow. CS installed a heave, pitch, and roll device in the engine room of the ship.
NOS processed the GPS data and computed the vessel's squat, trim, roll, pitch, and heading. The results indicate that the vessel's squat (dynamic draft), trim, roll, pitch, and heading were accurate to the 10 cm level using GPS. It was also demonstrated how a ship can be used to measure water level changes and water level values anywhere it travels.
The authors express their sincere appreciation to Chuck Coiner, Trimble Navigation, Ltd., Sacramento, California, and the Officers and Crew of the CGC BUTTONWOOD for their support and participation in this phase of the project.
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