Navigation and Seamanship

6.2.5. Ship-borne Radar

"Radar has proved to be an extremely valuable aid for position fixing and collision avoidance, but using it is not as easy as may appear at first sight. This is proved by the many strandings and collisions which have occurred involving radar equipped vessels.

Radar Bearings

"Radar bearings are subject to many possible errors and when trawling at long ranges from the coast, it does not take a large error to make the difference between making a good catch and losing the nets. Frequent comparisons should be made between visual and radar bearings of distant objects, and to see that objects right ahead of the vessel do appear on the heading marker.

Radar Ranges

"Fixing the vessel's position by means of radar ranges will be more reliable than using bearings, but the objects used must be positively identified. Of particular importance when fishing outside territorial waters, is not to mistake a line of hills inshore for the coastline.

Target Detection

"The probability of a target returning radar echoes will depend upon its size, composition, aspect or shape and background.

Size

"The strength of the echo returned will depend upon the reflecting area of the target.
"The maximum detection range will depend upon the height of the scanner and the height of the target. Under normal atmospheric conditions this will be in nautical miles. The formula is