RESTRICTED VISIBILITY NAVIGATION. Collision Avoidance In Restricted Visibility

RESTRICTED VISIBILITY NAVIGATION

Collision Avoidance In Restricted Visibility

Visibility may be restricted by heavy rain, snow, blown spray, low cloud, mist and fog, and in some parts of the world blown sand, and smoke.

Fog is defined as excess water vapour in the air, reducing visibility to 1 nautical mile or less.

Collision Avoidance In Restricted Visibility

Rule 19 Conduct of Vessels in Restricted

Visibility

(a) This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.

(b) Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel shall have her engines ready for immediate manoeuvre.

(c) Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules of Section I of this Part.

The rules of Section 1 apply in any condition of visibility. The particular rules are those appertaining to:

5. Lookout, 6. Safe Speed 7. Risk of Collision8. Action to Avoid Collision9. Narrow Channels10. Traffic Separation Schemes.

(d) A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists.

If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course, so far as possible the following shall be avoided:

(i) an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken,

(ii) an alteration of course towards a vessel abeam or abaft the beam.

(e) Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on her course.

She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.

Navigation In Restricted Visibility

Navigation

• It is important that during restricted visibility, that the position of the vessel is known at all times

• This is especially because of the lack of any visual references, unless the vessel is within sight of a navigational aid.

• This is also due to the lack of situational awareness that could come about about using the head up display on the radar, and manoeuvring as required by the Collision Regulations to avoid risk of collision.

Navigation

Parallel Indexing

• The principal method of monitoring navigation in restricted visibility is the use of parallel indexing

185 T

150 T

0.3 nm

0.3 nm

0.2 nm

• The Variable Range Marker is first set up on the same distance as is required to safely pass off the radar conspicuous object being used.

• In the example it is set up 0.3nm

• This is known as the cross index range

Parallel Indexing

• The Electronic Bearing Line is set up on the same bearing as the course that is required to be made good

Parallel Indexing

• It is important that the radar conspicuous objects used in parallel indexing are positively identified from the chart or chart plotter and checked on the radar.

• If parallel indexing is attempted on a moving object, it will lead you off course and possibly into danger.

Parallel Indexing

185 T

150 T

0.3 nm

0.3 nm

0.2 nm

• 1. The vessel is steered, so as to bring the radar conspicuous target against the Electronic Bearing Line.

Parallel Indexing

• If the target crosses and comes inside the Electronic Bearing Line alter to starboard to increase the distance off.

• If the target moves further away from the Electronic Bearing Line, alter to port to put it back on.

Parallel Indexing

• 2. The course is steered to keep the radar target on the line.

Parallel Indexing

185 T

150 T

0.3 nm

0.3 nm

0.2 nm

• 3. The vessel is now approaching the alteration of course point.

• The next course is 150 T, and cross index range 0.3’ .

Parallel Indexing

• 4. At this stage short of a catastrophic failure, the vessel will be safe, and the parallel indexing for the new course can be set up

Parallel Indexing

• 5. Set up the new cross index range (0.3 nm) on the Variable Range Marker, and then change the bearing of the Electronic bearing line to the new course (150 T) and rest it against the Variable Range Marker ring

Parallel Indexing

Parallel Indexing

• 6. When the Electronic Bearing Line on its new bearing of 150 T is about to come clear of the conspicuous object, alter course of the vessel to 150 T

• 7. As before, steer the course to keep the conspicuous radar object on the Electronic Bearing Line

Parallel Indexing

185 T

150 T

0.3 nm

0.3 nm

0.2 nm

• 8. Before the radar conspicuous object No.1 disappears astern, have available the new cross index range of Radar Conspicuous Object 2 available (0.2 nm)

Parallel Indexing

• 9. Set new cross index range on Variable Range Marker, and move Electronic Bearing Marker on bearing against Variable Range Marker ring.

• Steer to line as before

Parallel Indexing

• The use of parallel indexing need not be confined to restricted visibility, but may be used in clear visibility as well.

Parallel Indexing

Monitoring Course

• An additional method available for monitoring course is to preset routes into the chart plotter.

• These waypoints and routes should be preset into the chart plotter.

• The routes should then be verified during the periodic training so that there is complete confidence in these routes.

• The routes can then be used and relied upon in case of unexpected restricted visibility, night time navigation, and in transit on training or during an incident.

Monitoring Course

Sound Signals in Restricted Visibility

• Rule 35 • In or near an area of restricted visibility, whether by day

or night, the signals prescribed in this Rule shall be used as follows:

Sound Signals in Restricted Visibility

• (a) A power-driven vessel making way through the water shall sound at intervals of not more than 2 minutes one prolonged blast.

Sound Signals in Restricted Visibility

• (b) A power-driven vessel underway but stopped and making no way through the water shall sound at intervals of not more than 2 minutes two prolonged blasts in succession with an interval of about 2 seconds between them.

Sound Signals in Restricted Visibility

• (c) A vessel not under command, a vessel restricted in her ability to manoeuvre, a vessel constrained by her draught, a sailing vessel, a vessel engaged in fishing and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraphs (a) or (b) of this Rule,

Sound Signals in Restricted Visibility

sound at intervals of not more than 2 minutes three blasts in succession, namely one prolonged followed by two short blasts.

Sound Signals in Restricted Visibility

• (d) A vessel engaged in fishing, when at anchor, and a vessel restricted in her ability to manoeuvre when carrying out her work at anchor, shall instead of the signals prescribed in paragraph (g) of this Rule sound the signal prescribed in paragraph (c) of this Rule.

Sound Signals in Restricted Visibility

• (e) A vessel towed or if more than one vessel is towed the last vessel of the tow, if manned, shall at intervals of not more than 2 minutes sound four blasts in succession, namely one prolonged followed by three short blasts. When practicable, this signal shall be made immediately after the signal made by the towing vessel.

Sound Signals in Restricted Visibility

• (f) When a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit they shall be regarded as a power-driven vessel and shall give the signals prescribed in paragraphs (a) or (b) of this Rule.

Sound Signals in Restricted Visibility

• (g) A vessel at anchor shall at intervals of not more than one minute ring the bell rapidly for about 5 seconds. In a vessel of 100 metres or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel.

Sound Signals in Restricted Visibility

• A vessel at anchor may in addition sound three blasts in succession, namely one short, one prolonged and one short blast, to give warning of her position and of the possibility of collision to an approaching vessel.

Sound Signals in Restricted Visibility

• (h) A vessel aground shall give the bell signal and if required the gong signal prescribed in paragraph (g) of this Rule and shall, in addition, give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell. A vessel aground may in addition sound an appropriate whistle signal.

Sound Signals in Restricted Visibility

• (i) A vessel of 12 metres or more but less than 20 metres in length shall not be obliged to give the bell signals prescribed in paragraphs (g) and (h) of this Rule. However, if she does not, she shall make some other efficient sound signal at intervals of not more than 2 minutes.

Sound Signals in Restricted Visibility

• (j) A vessel of less than 12 metres in length shall not be obliged to give the above mentioned signals but, if she does not, shall make some other efficient sound signal at intervals of not more than 2 minutes.

Sound Signals in Restricted Visibility

• (k) A pilot vessel when engaged on pilotage duty may in addition to the signals prescribed in paragraphs (a), (b) or (g) of this Rule sound an identity signal consisting of four short blasts.

Sound Signals in Restricted Visibility

• (l) Notwithstanding paragraph (j), in the Canadian waters of a roadstead, harbour, river, lake or inland waterway, a vessel that is

• (i) less than 12 metres in length,(ii) built or converted for the purpose of pushing or pulling any floating object, and(iii) not located within a recognized mooring, storage or booming area

shall sound the signals prescribed for a vessel of 12 metres

or more in length.

Sound Signals in Restricted Visibility