Page 60 - Collision Avoidance Rules Guide

give-way vessel and the stand-on vessel should have used radar in
a fine crossing situation off the coast of Portugal. In the
Verdi-Pentelikon (US Court, 1970) the stand-on vessel was blamed
for failing to use radar in an area of dense traffic, such as the Straits
of Gibraltar, to obtain information regarding a vessel which had been
observed to be on a constant bearing on the port bow.
In regions of heavy traffic the need to use radar in good visibility
would apply to all vessels, but it may apply especially to ships fitted
with the more sophisticated radar systems which incorporate such
additional facilities as the ability to indicate whether there is risk of
collision with several targets and to determine the effectiveness of
proposed maneuvres. In such areas radar can be used to assess the
general traffic situation in all conditions of visibility.

Proper use of radar equipment
In the 1960 Regulations there was no direct reference to radar in any
of the actual Rules but recommendations on the use of radar infor-
mation as an aid to avoiding collision were given in an Annex. The
importance of radar for the purpose of collision avoidance has now
been recognised by incorporating the former recommendations into
the Rules to make them requirements. Rules 6, 7, 8 and 19 contain
specific references to the use of radar and there is an important
implied reference in Rule 5.
Proper use of radar to obtain early warning of risk of collision
requires that all controls should be at their optimum settings and that
the appropriate range scale should be used. In addition the choice of
display may be important. It has been generally recommended that a
stabilised display should be used where possible. This arrangement has
the advantage of enabling compass bearings to be read off directly, and
the echoes do not become blurred due to an alteration of course.
Where a true motion display is provided it should be used in
conditions favourable to this type of presentation. An alteration of
course made by another vessel moving at fairly high speed is likely
to be more readily apparent on the true motion display from the
change in direction of the echo trail. True motion is generally more
suitable for use with the lower range scales in congested waters
rather than in the open sea. On vessels fitted with two radars in close
proximity it may be advantageous to use the relative motion display
on one radar and the true motion display on the other.
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