Page 64 - Collision Avoidance Rules Guide

using radar and small errors in range measurement may also occur.
Further inaccuracy may result from the reading and plotting of
ranges and bearings. Several observations should be taken at short
and regular intervals to reduce the effects of these random errors
when there is a possibility of a close quarters situation developing.

Evje-Dona Evgenia

Basing what I am going to say upon those facts, I am unable to accept the
evidence of the Evje that initially the vessels were on opposite and parallel
courses. Accurate observations and plottings by the Evje should, in my view,
have revealed that the Dona Evgenia was in fact on a course which would
lead her across the line of advance of the Evje from her port to her starboard
bow. This initial error on the part of the Evje influenced her actions in rela-
tion to the Dona Evgeniu at a comparatively early stage, because, wrongly
supposing that the Dona Evgenia would pass her fairly closely to port, she
starboarded in the manner I have described, expecting thereby to pass the
Dona Evgeniu with ample clearance to port. A moment’s reflection upon her
navigation at this time is sufficient to satisfy me that, by making such alter-
ations to starboard in the circumstances I have just described, and in reduc-
ing her speed in the manner and at the times I have mentioned, she was in fact
putting and maintaining herself on a series of courses (which for this purpose
I may describe as an irregular arc) which brought her perilously near the line
of advance of the Dona Evgenia. It is little wonder therefore, that, after a
substantial alteration of course to starboard the master of the Evje found that
the bearing of the Dona Evgeniu had not changed as expected between the
time he first began to starboard and the time he completed his turn.
These facts, and the inferences which I have drawn from them, indicate a
lamentable lack of appreciation of the situation which was developing all the
time and which would have been obvious if accurate and simple plotting had
been resorted to. (Mr Justice Hewson, 1960)
When vessels are in sight of one another visual compass bearings
should normally give greater accuracy than radar bearings, but if the
vessel is rolling or pitching heavily errors may be present, especially
with the magnetic compass. Bearings taken relative to the ship’s
structure can be very misleading in determining whether risk of col-
lision exists. Assumptions made on the basis of scanty information
have been a contributory cause of many collisions in both clear and
restricted visibility.
In the case of Toni-Cardo (1972) it was established that the Cardo
altered course to starboard when the Tony had approached to within

45