A navigator's guide to visual cues and techniques - The Navigator Issue 37

As ships get bigger and bigger, and technology becomes ever more advanced, it might seem fair to ask whether there is still a place for ‘old-fashioned’ visual navigation techniques that rely on the human eye. Captain Marso Law AFNI from the Hong Kong Pilots Association argues that there is and shares lessons from his personal experience.

As navigators, we make the best use of all the latest navigational equipment on board. Lives, and ships, are much safer as a result. However, visual navigation continues to be a very important part of the range of safety precautions available to us. Colregs require every vessel at all times to maintain a proper lookout by sight and hearing, as well as by ‘all available means’ as appropriate. Making a full appraisal of the situation in this way is visual navigation at its most fundamental.

This is especially important when you are in a situation where there are many targets, such as fishing boats, tugs and tows, coasters, etc. Those targets on a steady or nearly steady bearing with you and getting closer are a collision risk, and you should apply Rule 7 of the Colregs as required.

It is good practice to use visual navigation techniques to monitor and crosscheck information coming from electronic equipment such as ECDIS and GPS. Just as it is vital to double check rudder angle indicators and engine repeaters, it is essential to check the input from the sensors is working in the way we want it to. GPS and ECDIS might be interrupted when passing under a bridge or be affected by a tall building nearby, for example. It can sometimes take digital systems a few seconds to accurately calculate speed over ground. One simple way to check whether you are still moving without instruments is that the engine wash comes to nearly the bridge front position when the ship stops over ground.

What to look for during visual navigation

Coastal navigation

Look out for landmarks that will help your navigation, such as leading lights, directional lights, lighthouses, beacons, building and cranes. Sometimes, buoys or even big trees or tall buildings on the coastline can help you monitor your ship’s position and speed.

A thorough passage plan taking into account all the surrounding landmarks as you make landfall will be very helpful. This allows you to plan your speed and angle of approach with reference to known coastal features. For example, look for the transit of two buildings at the point where you start altering course, and when you come into the transit of the leading lights. That way, you can be confident that you are on the correct track.

The length of the wash from buoy(s) is a useful indicator of the strength and direction of the tidal current. The direction of the ships lying at anchor, the weight and leading angle of the anchor chain and the drift of smoke from the funnel (not that there should be much, these days) all indicate the strength and direction of the wind and current.

If you always pass the same objects at the same distance, and you know how the ship typically reacts, you will immediately notice the difference if you are setting towards shallow water in strong wind and/or current.

Berthing operations

Looking at the tips of any cranes around you will give you an excellent indication of how the tidal current is acting at the basin, especially when the space available is restricted – which is often the case for today’s larger ships.

Make no mistake, the ECDIS and portable pilot unit (PPU) are both essential pieces for berthing and unberthing ships. Often, you cannot really see the water from the bow or stern of a 400m-long vessel! So, does that mean that visual navigational techniques are not useful for handling vessels of this size? Not at all.

If anything, we should have more landmarks around the turning basin to help visually identify anything which might have gone wrong. If your speed has not dropped as much as you expect, for example, you need to take early action to rectify the situation. Visual clues can help us recognise the need for that action in time.

Benefits and weaknesses of visual techniques

Visual navigational techniques do not rely on technology to work. They offer immediate feedback and can take in multiple targets – provided the visibility is good. Sometimes that information is not available in other ways. For example, with an eddy current, the existing equipment may not show the change in strength and direction of the current, but your eyes will tell you at once, and you can take action accordingly.

On the other hand, it is always harder to orient yourself or find sufficient input at night or in poor visibility. Your ability to judge depth and distance will be especially affected.

Open to all

Never think that it is only the senior pilot or captain who needs to know how to navigate visually. As with all other techniques, the more you notice and the more you practise, the better you will be. Some techniques take time to develop.

You can learn to judge speed by estimating your speed and position based on what you see from the bridge wing, and then compare it with what you see on the ECDIS or GPS. Always look out for navigational marks and transits for reference. All the navigational marks were put in place for a reason!

This technique applies mainly to shiphandling, but can also be useful in coastal navigation. You will be amazed how accurate it can be.

Better seamanship

It is very important to conduct a thorough risk assessment of your route before setting off, and plan accordingly. Add the information needed for different stages of the voyage – safe speed, landmarks for parallel indexing, contingency anchorages, areas where you will need to adjust your speed for heavy traffic density. Then add monitoring points, such as places for a visual check on the ship’s speed, or assessing the strength and direction of tidal current when passing certain buoys or beacons. Look at the strength of chain on anchored vessels to get a feel for the combination of wind and tidal current. Go outside the enclosed bridge to feel the wind, look out for other ships and check for other visual cues that could help keep you safe. Many people wait until the last minute to go outside the bridge, when it could be too late to make practical use of any visual cues you might pick up.

Looking ahead

Last but not least, safe navigation is the ultimate duty of everyone to secure the safety of lives at sea, protect the ship and operate responsibly on behalf of the owners of the ship and cargo, the environment and the port. Having a ‘feel’ for what you are doing is always important – if you feel something is strange, pay attention! Are you too fast? Off track? Is the ship behaving differently to how you would expect? Making the most of visual and electronic cues will help you find out.

As a young navigator, developing a good navigational routine, including visual navigational techniques, will certainly help you in your career. Navigators encounter different challenges every day. Working at sea is important and rewarding – and keeping up with your knowledge and studying visual navigational cues to help increase the safety margin and improve your skills at sea will help keep it that way.