Navigational Equipment

The Merchant Shipping (Navigational Equipment) Regulations 1993 require certain ships to be provided with a magnetic compass installation and other specified ships to be fitted additionally with a direction finder, an echo sounder, a gyrocompass, radar and ARPA installations, a speed and distance measuring installation and a rate of turn indicator.

Collisions have been caused far too frequently by failure to make proper use of radar and ARPA in both restricted visibility and in clear weather. A common error has been altering course on insufficient information and by maintaining too high a speed, particularly when a close quarters situation is developing or is likely to develop. Information provided by radar and ARPA/ATA in clear weather conditions can assist the watch-keeper in maintaining a proper lookout in areas of high traffic density. It is essential for the observer to be aware of the current quality of performance of the radar (which can most easily be ascertained by the Performance Monitor) and to take account of the possibility that small vessels, small icebergs and other floating objects such as containers may not be detected. When video processing techniques are employed, caution should be exercised.

Echoes may be obscured by sea or rain clutter. Correct setting of clutter controls will help but will not completely remove this possibility. When plotting larger targets on a medium range scale, the display should be periodically switched to a shorter range, and the clutter controls adjusted, to check for less distinct targets.

The observer must be aware of the arcs of blind or shadow sectors on the display caused by masts and other on-board obstructions. They must be plotted on a diagram placed near the radar display, which must be updated following any changes, which affect the sectors.

The radar display should be kept on at all times when weather conditions indicate that visibility deteriorate, and at night wherever fog banks, small craft or unlit obstructions such as icebergs are likely to be encountered. This is particularly important when there is a likelihood of occasional fog banks so that vessels can be detected before entering the fog. The life of components, and hence the reliability of the radar, will be far less affected by continuous running, than by frequent switching on and off.

In restricted visibility the radar display should be permanently on and observed. The frequency of observation will depend on the prevailing circumstances, such as own ship’s peed and the type of craft or other floating objects likely to be encountered.

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International Regulations for Preventing Collisions at Sea

The prevention of collisions at sea is a matter of concern to all nations. “International Regulations for Preventing Collisions at Sea” were internationally accepted and came into force in 1972.

The Regulations define what vessels and what waters the rules apply to, and spell out the meaning of basic terms. They deal with lights, the shapes of visible distinguishing marks to be displayed by different categories of vessels in various circumstances, sound signals, and the rules for conduct in restricted visibility. Since it is in thick weather that any collisions and stranding take place, the latter rules are extremely important.

The Regulations embody the steering and sailing rules to be followed when vessels are in sight of each other. These rules form the heart of what is known as “The Rules of the Road” for power-driven vessels.

Some rules deal with sound signals for use when vessels in sight of each other alter course to port or starboard, distress signals, the essential need for constantly keeping a good-look-out. The Annex lays down a code of practice for the use of radar information as an aid to avoiding collision at sea.

It is necessary to memorize the crucial rules, and to understand their gist. For example, one rule requires that when two vessels are meeting end-on, each should alter course to starboard, so that each may pass on the port side of the other.

Another rule states that when two power-driven vessels are crossing, so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way of the other. It is clear from Regulations that the stand-on vessel (i.e. the one having right of way) should normally maintain her course and speed, while the seaman is instructed that the vessel, which must keep clear, should slacken speed, stop or reverse, if necessary in order to keep clear. One of the rules requires an overtaking vessel to keep clear.

The International Regulations cannot prevent all collisions, since ships are handled by men, and men can make mistakes or errors of judgment. But strict adherence to the Regulations will always reduce the likelihood of disaster.

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