The Complete 8th Edition Yachtmaster

No matter what the weather conditions, as soon as you enter a strange harbour or become involved with any close-in work around narrow channels, detailed chart-table navigation becomes impractical and GPS at least partially inappropriate. As the yacht threads her way through navigable gaps that are measured in yards rather than miles, the time involved in taking fixes and plotting carefully constructed courses to steer renders such techniques unusable. Even if you tried to make time by detailed planning, you would be unwise to trust a course based upon published tidal stream prediction when an error measured in boat’s lengths could spell disaster.

Theoretically, one could be forgiven for imagining that a series of shrewdly plotted waypoints arranged as a route might work perfectly so long as Selective Availability remains removed from civilian GPS. Unfortunately, the juxtaposition of concepts as you move from eyeball to screen and back again can cause such a culture shock that, in tight situations, practical steering errors occur at vital corners. Furthermore, the plotting accuracy required to place a waypoint exactly on a gap in the rocks three boat’s lengths across on a paper chart may well prove beyond the limits of your pencil sharpener. Finally, if the GPS readout happens to be set to the wrong datum for the chart, the whole exercise is reduced to a dangerous farce. As we shall see, GPS can have its uses in pilotage, but it does not supply an easy overall answer. You must therefore first look for signposts that may readily be observed visually in preference to textbook data or electronics. The arts that result are known as pilotage.

The essence of successful pilotage is to extract the information from chart and pilot book that will enable you to work through the dangers on a series of positively defined straight lines. Each line takes you past one problem or another, until you either arrive at your destination, or sail safely out into wider waters.

So long as you are on a safe line, or tracking through a defined zone that is obviously clear of danger and that leads you to the next line, you do not usually require to know how far along it you are. Thus, in pilotage, your position is often defined only in the dimension of your desired track. The cross-reference that would constitute a fix is generally absent (see Fig 23.2), except at certain important times. Coming to terms with this is vital to competent pilotage. An examiner can always tell a tyro because of the way he is constantly trying to fix his position, even when to do so is not only unnecessary and a waste of time, it is also nigh on impossible.

Because of the presence of cross-currents in much pilotage, it is rarely sufficient simply to steer so that the yacht’s head points towards the next object. Fortunately, there are a number of wrinkles for making sure that the boat remains on the desired line without having to resort to fixing.

Two types of line are essential to the business of pilotage (Fig 23.1): the safe track, which is the straight line leading through a particular set of dangers; and the clearing line, defining the edge of a danger area. Keep on the right side of a clearing line and you are safe; venture across it, and you are stranded.

The best way to establish the whereabouts of either type of line is with a transit. As we have seen in Chapter 18, the line joining two known objects, projected seaward, is the most reliable position line of all. When used to mark off a safe track you can work along it with no difficulty, and you can see straight away if you depart from it by as much as a cockpit’s width. A transit works equally well if you are steering directly towards or directly away from it and it makes a fine ‘leading line’ for entering or leaving a harbour. For this reason, many authorities set up transits using posts and lights in crucial places. These are charted and noted in all relevant pilot books.

Fig 23.1 Safe pilotage. Above: a safe track. Below: a clearing line.

Planning is vital for close-in pilotage where situations can develop rapidly. All hands are looking out here on a windy day and have just spotted a hidden buoy. Relief is tangible.

In addition to indicating safe tracks, transits also make fine clearing lines. If the two markers remain ‘open’ on the correct side, all is well; if they close, you are on the clearing line; if they open on the wrong side, instant action will be required if you are to continue having a happy day.

We have looked at many forms of transit in Chapter 18, but in pilotage you can be especially creative. If no ‘official’ transit lends itself to your needs, inspect the chart carefully for two recognisable objects that, when in line, will give you the safe passage or the clearance you are seeking. It will surprise you how frequently something will show up. It could be the end of a pier and a conspicuous hotel, two islands with their edges just ‘closed’, the right-hand side of a building ‘on’ with a light structure, etc. The best method of finding them is to lay your protractor along the desired track on the chart, then see what you can spot along its edge. You may have to shunt it around a little, but there is frequently something that will serve.

If you cannot make up a transit to lead you from one mark (a buoy, perhaps, or a post) to the next, your second line of defence is to use a compass bearing. This is an indifferent substitute for a charted transit, but you can still use natural transits to make the best of the situation. Immediately after rounding the first mark, steer the boat directly for the second. If you cannot instantly identify it, ask all hands to look for it dead ahead. As soon as you have it, glance astern at the first mark to ensure you have not already been set off the safe track. Now line up your goal with anything immediately behind it that is not going to move. A fisherman mending his nets will do so long as he doesn’t walk off. Keep the buoy and the fisherman in transit and you can only be on the direct line from the first buoy to the second.

If you cannot find two objects to line up, you will have to use your handbearing compass, which is a pilot’s last resort. When you are sailing away from a known object down a safe track defined by a compass bearing, you can keep on track by using a back bearing. Watch the object over the compass as its distance increases, and make sure that its bearing remains constant. The preferred technique for achieving this end is to hold the compass at the desired bearing and see if the object moves to the left or right. When the boat wanders from her track it is easy to decide which side you have slipped if you are using the compass like this. If you sight the actual bearing of the object and try to work out which way you have drifted by doing sums in your head, you can easily come unstuck.

Always remember that the best compass you have is the ship’s steering compass. If you are sailing towards a specified object on a safe track – or if an object whose bearing defines a clearing line is almost ahead – you have only to read the compass when the boat’s head is exactly on the object to determine its precise bearing, given, of course, that you correct for any deviation. If the object lies more than a few degrees off the bow, you can always ‘twitch’ your heading every so often to check its bearing on the steering compass. This technique can save considerable trouble trying to use a handbearing compass when there is no need.

If an object defines a safe track and you are steering directly towards it, the trick for remaining in line is the same as that used for a back bearing with the handbearing compass. Keep your heading constantly on the safe bearing. If the object drifts away to one side, it should be easy to decide which way to correct so as to set you back on track. Make a positive ‘jink’, then put your ship’s head back on the safe bearing. Note the relationship of the object to your heading, and retry if necessary until you get it right.

There will be occasions when your only useful source of input is the echo sounder. Don’t despise this. We’ve already looked at how it can supply a position line of a sort, and there are many occasions when you are rounding a shoal that is not steep-to when a depth is all you need – and indeed, all you have – to ensure safe passage.

Sometimes a particular track will remain safe until you have run to a given point at which you must alter course. In these situations, always look for an unambiguous visual definition to tell you when you have arrived. This could be a transit closing abeam of you, or an object coming on to a certain bearing. It might be a depth on the echo sounder, or, less accurately, a single object directly abeam. The time when something is exactly abeam can best be judged by looking down the mainsheet traveller. It is as good as a primitive gunsight.

If no visual cut-off point presents itself, see if you can work in an easy-to-use GPS position line. GPS reads out in Latitude and Longitude, both of which are no more than lines of position. Sometimes you can define the point to leave a safe line as the moment you pass a certain meridian or parallel. A typical instruction would be: ‘Stay on the transit of Brown Cow Rock and Farmer Giles’ gable end until the latitude racks up to 50° 43.15N´. So long as the safe track is making a reasonable cut with the chart grid (see Chapter 18, Position Fixing) this technique is convenient and accurate, but you must check your GPS datum.

Fig 23.2 Straight line pilotage. The pilot only knows his exact whereabouts when one of his straight lines intersects with another at a point-of-course change.

Often, a safe track is broad and straight, but surrounded by ghastly nasties below the surface of the water. Try to think of such a track as a safe corridor. Define both walls of the corridor with clearing lines of some sort, keep inside them, and you have nothing to fear. Where no clearing lines can be found, and you can be absolutely certain of the position of a suitable single waypoint plotted smack in the centre of one end of the corridor, you might in extreme circumstances venture into the corridor on the safest track to the waypoint. Now work towards or away from it (straight down the middle) using cross-track error to fill in the shortfall. This means commit ting to a course of action with your colours nailed to a single source of information that cannot be cross-checked, so you have chosen to break the first law of navigation. If the GPS should fail halfway along the line, you may have little choice beyond anchoring or trusting in the Lord to find you a safe route out.

In larger-scale pilotage, GPS can also supply a clearing line where no visual object can be discerned. If a distant beacon is too small to see, even with binoculars, plot it as a waypoint and note its changing bearing just as you would a visual compass bearing. If no beacon exists, plot an ‘abstract’ waypoint at the most suitable place from which to run a safe bearing.

Make sure you have an instant contingency plan for electronic failure.

Triple-check everything you pre-plot and double-check your datums, because this close to danger these become critical.

Determine whether your GPS is reading out in Magnetic or True degrees, because most have the facility to deliver either and the difference can spell disaster.

On the face of things, an electronic chart plotter delivers all the answers to inshore pilotage. You can actually watch the boat as she jinks among the rocks to a safe haven. Very nice in theory. One danger is that an over-zoomed electronic chart may be a fool’s paradise, and it is easy to over-zoom without noticing because unless you do so there may be insufficient scale to see what’s really going on. Furthermore, while you can rely on a set-up transit because it was put there by pilots who certainly knew what they were about, trusting the plotter is putting your faith in everything on the chart. Among the reefs, it is possible that the survey may be less complete than a zoomed chart suggests. In any case, if the GPS is a couple of boat’s lengths out or there is some issue with the datum (which there shouldn’t be, but which I have certainly seen), following the silver screen could lead to your Nemesis.

If you do decide to use the plotter, make sure you have a ready exit strategy in case of sudden failure.

Having delivered such a catalogue of dire warnings, I must say that I often use a portable plotter in the cockpit to back up what I am seeing with my own eyes. Very reassuring it can be, too.

It should be impossible for a chart plotter to get its datum wrong, but it isn’t. This real photograph shows the boat 300 yards from where she really was. Think about this before committing to a plotter for close-in pilotage.

Because your affairs may develop rapidly when you are engaged in this type of work, it is helpful to prepare a plan in advance. Your pilot book will sometimes do this for you, but more usually you must deal with the question yourself. The form taken by these plans is highly individual, but they should contain such information as courses, bearings and approximate distances from one mark to the next. It may also be useful to know how much tide has risen above chart datum at any given moment, so fill out your tidal curve and keep that handy as well. The information will stand you in good stead, particularly if you have to modify your plan during its execution, so that you end up somewhere you did not intend to go. If you have a well-thought-out plan at hand when the action starts, you are under far less pressure to dive below and start fumbling around with the plotter.

Ideally, you should ask someone else to steer while you are piloting. Your sole task is then to con the vessel using your plan and the chart. This way it is easy for you to call the shots on the sailing of the boat, as well as keeping her off the bricks and the putty.

Always remember that you have much less control over your boat’s direction of travel relative to the seabed with a following tide than you have with a foul tide. When the current is strong and foul, small course alterations bring you a big dividend in terms of sideways tracking. At night particularly, you must be doubly vigilant about these effects.

Take your time, and never hesitate to stop altogether if you become disorientated. Once you are anchored, or hove to, or simply not going anywhere any more, you can shed the stress, then plot an accurate fix before collecting your thoughts for a fresh start.

SKIPPER’S TIPS	Instant position lines
The one thing you won’t have time for when things are developing fast is fixing your position on the chart. Even if you could manage to bang one down, you are usually moving so rapidly relative to the scale of your surroundings that a fix is yesterday’s news by the time it has been plotted. In these circumstances, the less you use the handbearing compass the better.
Fortunately, there are numerous sources of instant position lines close to the shore. There’s the steering compass for observing objects directly ahead, astern or abeam, and there’s nothing to stop you pre-measuring all sorts of angles on the deck of the boat, then adding or subtracting these from the ship’s head. Note the angles of, say, the forward shrouds, the aft shrouds, a particularly useful stanchion, and so on, from the steering position or the companion way. Bearings thus obtained will be rough, but they are always ready.