Evaluation of Environmental Condition Using Marine GPS

Shigeyuki Okuda and Yasuo Arai

Abstract:	Now, the position accuracy of GPS is about 100 m (2drms) by the effect of SA. But marine users usually get their position by 2-dimensional positioning using fixed antenna height. Furthermore, if they utilize a method of all in view that becomes popularly in latest receiver, then it is said that its accuracy is improved and is better than 100 m under SA. Therefore, GPS has best accuracy in radionavigation systems off the shore, and has popularized worldwide. However, there is a problem concerning the position accuracy in the water accepted the effect of topography or structures such as harbor and harbor approach which are close to arrival and departure of sailing by stages. In this paper, we developed the evaluation system concerning the environmental condition in addition to the regional restrictions and tried to apply the system to the real sailing condition. First, this system determinates the environmental condition of receiving signal, namely the effect of shading by topography and structures on land, own ship, and other ships. The system prepares the database of the environmental condition and carries out nmeric calculation actually. We propose the method of modeling these configuration to evaluate adequately against topography and structures. Next, the system calculates the alert using this database and own ship’s schedule, specifies satellites in the field of view, and calculates DOP. Finally, the system predicts the position accuracy using DOP and the error in the range measurement concerning planned sailing, and judges to be any restrictions. If there are any restrictions, we will have to reconsider a positioning method or the sailing time. This evaluation system is able to apply to any kinds of ship or any waters by replacing the configuration database, and will be able to examine the environmental condition which satisfies the required accuracy in the specific water.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	317 - 324
Cite this article:	Okuda, Shigeyuki, Arai, Yasuo, "Evaluation of Environmental Condition Using Marine GPS," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 317-324.
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