Abstract
Hyperbolic navigation methods for the 100kHz band are widely used for fixing the position of a ship. With the increased use of Loran-C navigation system, the positioning errors near seashore have become a problem for many fishing boats and small vessels. We measured the errors of the phase of Loran-C wave for normal incidence to coastline in Shibushi-Bay, Kagoshima. As the interference occurs between the incident and the reflected wave, the curve of the phase error becomes sinusoidal-like variation. It is shown that the experimental result is explained fairly well by numerical calculations. In this paper, the phase error is discussed with relation to the incident angle. It is found that at angle of 45°the reflection from the coastline appears to be very weak and the reflection strong at highly oblique incidence. As the usual ship-borne Loran-C receiver indicates time difference in units of 0.1μs, the region where the phase error becomes larger than ±0.1μs is considered to be significantly affected by the reflected wave from the coast. These distances from the coastline are as follows : about 2km for near normal incidence, 300m for 45°, and more than several km for 60°-75°.
