Effect of LORAN C wave propagation on land and preparation correction chart based on its evaluation.

Abstract

The LORAN C is a radio navigation aid system operated by the Coast Guard of the U.S.A., using long waves to measure the position of ships and airplanes. It gives hope for the usable range of ground waves allowing stable propagation up to a radius of 2,000 km from a LORAN C station and permits a high-accuracy use over a wide area. However, a systematic error is caused in measured results if land is included in the wave-propagation route, and the accuracy of position measuring becomes lower. In this report, we analyze data from the LORAN C regarding the North-West Pacific chain that were obtained by the survey ship “SYOYO” during navigation in the sea south of Hatizyo island and from Simizu port via Nozimazaki coast to Hatinohe coast. Also, the effects of land propagation waves included in incoming waves are evaluated and the preparation of the correction chart of the same chain in the Japanese waters based on the analyzed results are described. Evaluation results (1) As a propagation speed of LC waves in the sea, 299. 715 m/ μs (greater than the conventional value, 299.691 m/μs) is suitable. (2) The propagation speed of waves on land is less than that in the sea, and the wave-propagation time increases by 6 ns/km compared with that in the sea. A conversion of this value to the wave- propagation speed corresponds to 299. 18 m/ μ s.