Why use 20 LoA to distinguish between unwanted 'boat clutter' and wanted collision avoidance data?

This question was asked by Capt. Grahame A. Burton, Vice President, Fleet Services Division, Princess Cruises. Capt. Burton suggested that there may be an already established size limit in the Collision Regulations that would be more appropriate.

I asked Gordon May, National Program Specialist, Marine Communications & Traffic Services, Canadian Coast Guard if he felt there was better criterion than 20 m LoA to separate unwanted 'boat clutter' from wanted collision avoidance data and if MCTS required boats over 20 m to report in. Here is his response:

From: <MayGord@DFO-MPO.GC.CA>
To: <fpot@home.com>
Subject: RE: Recommendations for Integration of AIS into Bridge Operations
Date: Monday, October 30, 2000 07:21

Fred:

20 m LoA is also the criteria used for the TSS (Colreg Rule 10 Canadian
Modification)

MCTS - Canadian VTS Regulatory application is as follows
3. (1) Subject to subsection (2), the VTS regulations apply in respect of

  1. every ship twenty metres or more in length;
  2. every ship engaged in towing or pushing any vessel or object, other thanfishing gear, where
  1. the combined length of the ship and any vessel or object towed or pushed by the ship is forty-five metres or more in length, or
  2. the length of the vessel or object being towed or pushed by the ship is twenty metres or more in length.
(2) These Regulations do not apply in respect of
  1. a ship engaged in towing or pushing any vessel or object within a log booming ground;
  2. a pleasure yacht that is less than 30 m in length; and
  3. a fishing vessel that is less than 24 m in length and not more than 150 tons gross tonnage.


So In light of all of the above it would seem that 20 m could be the most
likely recommended parameter.

Regards

Although these critria are more realistic than the simple, single criterion recommended, they would be more difficult to implement, not only from a technical view point but also and, more importantly, it would be more difficult to train the OOW on the effects of electing to exclude 'boats' from the ECDIS/Radar screen.

So far (October 30, 2000) it seems that everyone agrees that 20 m LoA is an acceptable criterion.