Barry Young is shown Bolton’s diagram of his Rule of Thumb

Barry Young is shown Bolton’s diagram of his Rule of Thumb – the method of extending line of sight to the background behind the other approaching vessel to assess Risk of Collision.
B Young – “You have based quite a lot of your evidence about changing bearings by lining up the vessel with the land behind, now that method is wrong. It’s inaccurate & it’s never taught in our navigation school & I can understand that you are going to try & show that it is true but I think we could waste a lot of time. The Collision Regulations clearly say that you’ve got to watch the compass bearing of an approaching vessel to assess the risk of collision.
Bolton – “Rule 22.7.1 says Every vessel must use all available means appropriate to determine if Risk of Collision exists. Rule 22.7.4(a) says Such risk must be considered to exist if the Compass Bearing of an approaching vessel does not appreciably change. It doesn’t mention a Relative Bearing which fails if the user’s vessel doesn’t keep a straight course. This Rule of Thumb method, I’d say is almost better than the compass because in some situations a compass may not be available & you’ve got to do it any way, as anyone does even if they’re not on a boat. Crossing a road & seeing oncoming traffic, natural in a dinghy when you haven’t got a compass or fixed objects. We all use this exact method looking at something coming towards us & its passage on a background.
B Young – “Mr Bolton, we don’t all use that & I would fail any candidate that suggested to me that he could determine risk of collision by watching land in the background. If we had half an hour I can prove to you that it is not a valid method of assessing risk of collision & it’s not mentioned in the collision regulations.
The Judge – ” Thankyou Mr Bolton. that’s your time.”
In the post 16 Jan’14 –
“Barry Young again appears to have breached his Code of Conduct in his Brief of Evidence in his denial of validity re what Bolton calls an “Infallible Rule of Thumb,”
Paul Bosier in “Learn the Nautical Rules of the Road” gives Bolton validity, very clearly explaining “A useful technique to check the other vessel’s movement against the background” See Post 18 Jan.
This book is available at
Farwell in his “Rules of the Nautical Road” also gives Bolton further validity “The human eye is still the most effective watchkeeping aid. Eyeballing is ,with constant practise, an effective & reliable skill … to judge distances by eye, inclinate on other vessels & mentally calculate the closest point of approach …an intuitive use of the compass to asses bearing movement.”

The diagram illustrates how this Line of Sight method is used & how highly accurate it is.

For comparison the Relative Bearing method is shown with the
essential requirement that the vessel using it must keep a straight course –
if a relative bearing doesn’t appear to be changing much,
it’s probably because that vessel is turning towards the vessel
being observed as in the case of the ferry observing Classique

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