Surface current measurement of sea using VHF radar on vessel; Effect upon antenna pattern

In order to measure the flow velocity field in coast, VHF(Very High Frequency) radar is often used recently, because it enables to obtained the velocity distribution in extended wide region simultaneously. The array antenna is needed fairly large area to operate the radar and it should be located at particular place such as a spot with sweeping view. Another type of the radar, loop antenna with monopole produced by CODAR, is small and useful for the measurement. If it can be used on board a moving vessel, the possibility of ocean field measurements will be extended extremely. However, it is obviously difficult to operate the radar on a steel vessel, because it affects extraordinarily. It should be considered that the vessel is a part of the radar. This paper describes the result of examination on inference of the radar on the steel vessel, using VLCC (Very Large Crude-oil Carrier). Although the characteristics of the receiving wave, called "antenna pattern" here, is deformed very much, it is possible to estimate the arrival directions of the radio waves in particular region. The result shows the possibility of measuring the flow velocity distribution by means of the VHF radar on the vessels.