Report on the Joint
Coast Survey and National Geodetic Survey
Centimeter-Level Positioning of a Marine Vessel Project
"The U. S. Coast Guard Buoy Tender Test"
David B. Zilkoski, J. Don D'Onofrio, Rudolf J. Fury, Curtis L. Smith
National Geodetic Survey
Dr. Lloyd C. Huff and Barry J. Gallagher
With the availability of high-accuracy, differential Global Positioning System (GPS) results in real-time, there is a new opportunity to use GPS to accurately measure a marine vessel's dynamic draft (settlement and squat) and 3-D attitude (roll, pitch, and heading). The National Geodetic Survey (NGS) and the Coast Survey (CS), offices of the National Ocean Service (NOS), National Oceanic and Atmospheric Administration, propose to transfer this technology to the Port Authority of Oakland, California. NOS would provide the technical personnel to set up and conduct a demonstration of this application on large marine vessels operating in the Port of Oakland. The overall goal of this project is to provide the position of a vessel's keel in real time to within 10 centimeters (about 4 inches) relative to the bottom of the shipping channel.
In support of the project, there were three meetings (July 15, October 23, and December 20, 1996) hosted by the Port of Oakland and NOS to discuss the real-time positioning of vessels project. On December 3-4, 1996, CS, NGS, Trimble Navigation Ltd., and the U. S. Coast Guard (USCG) performed GPS tests on a USCG buoy-tender ship. GPS data were used to compute the vessel's dynamic draft and 3-D attitude. 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 TSS-335B vertical reference unit (to measure heave, pitch, and roll) in the engine room of the ship.
NOS processed the GPS data and computed the vessel's dynamic draft and 3-D attitude. The results indicate the linear equivalent to the vessel's dynamic draft and 3-D attitude were accurate to the 10 cm level using GPS. It was also demonstrated how a ship can be used to measure local water-level changes and actual water-level values everywhere it travels.