Analysis of Radar Echoes of the Overhead Power Line and The Small Boat at Kurushima Kaikyou

Abstract

When a vessel proceeds toward an overhead power line (or cable), its radar receives the radar reflected waves from the overhead power line and the echo appears on the radarscope as a single echo from a small boat always at right angles to the line of the cable. Generally it is known well that this echo appears on the radarscope. However the sufficient comparative evaluation is not carried out about the characteristics of the radar reflected signal from the overhead power line and the small boat. In this paper we examine the characteristics of radar signal intensity and angular size of both echoes by the comparison of the theoretical analysis and the actual observation results which was executed at Kurushima Kaikyou. The results clearly identifies as follows: 1. The echoes of small boats are more likely to appear on the radarscope, at a distance of 300m or less from the overhead power line, than the echoes of the power line. 2. The echoes of the overhead power line are more likely to appear on the radarscope, at a distance of 900m or more from the overhead power line, than the echoes of small boats. 3. The angular size of echoes suits closely the antenna reception pattern which is given as a function of azimuth angle and threshold level.