Disturbances of 100-kHz band Decca waves caused by a large bridge

Hyperbolic navigation methods in the 100-kHz band are normally used for fixing the position of a ship. Because many large bridges have been built in recent years, an analysis of the positioning error caused by these bridges is required. From experiments and theoretical considerations for Decca waves near the Minami-Bisan Seto-Ohhashi Bridge, it was confirmed that the main sources of the secondary wave are the two main towers of the suspension bridge. It was also shown that the bridge can be assumed macroscopically as a pair of vertical electric dipoles with a static capacitance of approximately 0.2 /spl mu/F.