Pilotage Planning for Harbours - Safe Coastal Entry Guide

Prerequisites

• Position Fixing: bearings, transits, cocked hats and the use of a hand-bearing compass.
• Course Plotting and Tidal Navigation: heights of tide, under-keel clearance and tidal streams.
• Recognition of IALA Region A buoyage (lateral, cardinal, isolated danger, safe water and special marks) and light characteristics, from Competent Crew and Day Skipper theory.
• VHF operation at SRC level is strongly recommended (the SRC is the legal minimum to operate a set on a UK vessel).
• Day Skipper Practical candidates should have 5 days and 100 miles at sea, theory to Shorebased level, and be at least 16.

Learning Objectives

By the end of this lesson you will be able to:

• Explain what pilotage is and how it differs from chart-table navigation.
• Prepare a concise pilotage plan for a harbour entry by day and by night.
• Use transits, leading lines and clearing bearings to stay in safe water without constant fixing.
• Use sector lights and identify lights by their characteristics.
• Use the echo sounder as a pilotage check.
• Plan abort points, a point of no return and contingency anchorages.
• Make and monitor the correct VHF calls on entering a port.
• Recognise and avoid the common pilotage errors.
• Calculate the tidal window over a bar and the heading needed to hold a leading line in a cross-stream.
• Brief the crew and use electronic aids as a cross-check on, not a replacement for, the visual plan.

RYA Day Skipper Shorebased syllabus items covered (Pilotage): preparing a pilotage plan from chart, almanac and pilot book; use of transits, leading lines and clearing bearings; echo sounder as a navigation aid; light characteristics, sector lights and night entry; IALA Region A buoyage; harbour VHF procedure and port signals; abort points and contingency anchorages. Practical items: entering and leaving harbour by day and by night, and briefing the crew.

What Pilotage Is

Pilotage is navigation by eye in close proximity to danger — entering and leaving harbours, threading a channel, passing between rocks. Things happen too quickly for plotting fixes on a chart: in a narrow entrance a yacht at 5 knots covers a cable (0.1 mile) in just over a minute. The skipper must therefore do the thinking in advance, at the chart table or at home, and on deck simply execute a plan using visual references that can be checked in seconds.

A good pilotage plan answers four questions for every leg:

1. Which way do I steer, and what will I see ahead to steer for?
2. How do I know I am still in safe water (clearing lines, depths, marks)?
3. How do I know when to turn?
4. What do I do if it goes wrong?

Sources for the Plan

• The largest scale chart of the area (paper or electronic, zoomed in correctly).
• Pilot books and almanac harbour pages: entry directions, leading lines, VHF channels, traffic signals, hazards, berthing.
• Tide tables and tidal stream data — for depth over bars and the direction the stream sets across the channel.
• Notices to Mariners and local harbour notices: dredging, new marks, changed buoyage.
• Photographs in pilot books, to recognise marks from seaward.

The Pilotage Plan Format

The plan must be readable at a glance, on deck, in rain and spray. Use a single side of paper (or a laminated card or a page in a waterproof notebook), sketch-style, with bullet points — not paragraphs.

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A typical plan contains:

Many skippers draw a "ladder" or sketch: the track drawn straight down the page, with each leg's heading and distance on it, and the marks drawn to the left or right as they will be seen.

The RYA approach: keep it simple

The RYA Day Skipper practical course notes give four rules for pilotage that are worth writing at the top of every plan:

• Plan before you leave. It is easier done stationary at the chart table than heeled over at 20 degrees and feeling seasick. Simplify the chart to the main points needed for entry and exit.
• Let someone else helm while you pilot, so that you have time to look at the plan, look around and make decisions.
• Speed: the boat should travel slower than the speed at which you can make decisions. Think two steps ahead, and if you need to, slow down to assess the situation.
• Use several independent checks. In the notes' example of leaving Porth Dinllaen, where the danger is a rock awash north of the anchorage, three checks are planned: a waypoint placed on the rock with a proximity (arrival) alarm set to 400 yards, so that if the alarm sounds you stop or alter course; a clearing line taken from the flagpole on the Coastguard lookout; and the 10 m depth contour, which once crossed confirms that the rock has been cleared.

For a buoyed channel through sandbanks, such as the Caernarfon Bar in the same example, the advice is to plot a course from buoy to buoy and cross each one off as it is passed. A buoyed passage looks simple, but it is easy to miss a mark and drive onto a bank, especially where cross streams run at the entrance. Draw the expected cross streams on the plan as a reminder, and keep the next buoy in transit with the land behind it so that you can see at once if you are being set sideways.

Transits and Leading Lines

A transit is two fixed objects seen in line. It is the pilot's most powerful tool: it gives an exact position line with no compass error, and you can see instantly if you are drifting off it.

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Natural transits use features such as the edge of a headland, a prominent tree or hilltop, a house or a chimney. Artificial transits use beacons, buoys (with caution, as buoys move) or purpose-built leading marks.

Leading marks

Many harbours have leading marks or leading lights: a front mark low and near, a rear mark high and further away. When they are vertically in line, you are on the safe leading line.

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If the marks open, steer towards the front mark to get back on line — the "follow the front mark" rule: if the front mark appears to the left of the rear mark, you are to the right of the line; turn left, towards the front mark, until they are back in line. Keep the marks in line by adjusting heading; with a cross-tide your heading will differ from the line's bearing, and that is fine — the transit tells you the ground track, which is all that matters.

Back transits

A transit astern (a back transit) works just as well when you are leaving a harbour or when there is nothing suitable ahead. Write in the plan whether a transit is ahead or astern.

Clearing Bearings

A clearing bearing (clearing line) is a bearing on a charted object which keeps you clear of a danger, so long as the bearing stays on the correct side of a pre-planned value. It saves you constantly fixing.

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How to plan one

1. On the chart, draw a line from a conspicuous object, passing just clear of the danger on the safe side, with a margin.
2. Measure its bearing and convert to Magnetic.
3. Work out which side is safe: write it as "Keep the spire bearing more than 270 degrees M" (or "not less than", "not more than").
4. On deck, take regular bearings with the hand-bearing compass (held clear of the engine, winches and steel fittings, as described in the Position Fixing lesson). If the bearing approaches the limit, alter away.

A tip for the safe side: imagine standing on the boat looking at the mark; if the danger is to the left of the line and the bearing increases as you move right, then "more than" is safe. Double check on the chart.

A clearing line may also be a transit — "Keep the lighthouse open to the right of the headland" — which needs no compass at all.

Using the Echo Sounder

The depth sounder is a continuous position check. Pre-calculate the expected reading at each stage of the entry: the charted depth plus the height of tide at your ETA (allowing for how your instrument is set up — depth below transducer, below keel, or below the surface).

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Useful techniques:

• Following a contour. In some estuaries you can follow a depth contour along the edge of a channel, e.g. "keep depth above 5 m".
• Confirming a turn. A steep shelf or a dredged channel edge marks the turning point.
• Alarm setting. Set the shallow alarm to your minimum safe depth.

A reading much shallower than expected means you have left the channel or are not where you think you are: stop, slow down, or turn back towards known deep water.

Tidal Streams and Depths in an Entrance

The tide affects a harbour entrance in two ways: it changes the depth and it moves the boat sideways. Both must be in the plan.

Depth over a bar or sill

Work from the chart datum depth, the height of tide at your arrival and the draught of the boat, with a safety margin.

Example. The bar is charted at 1.2 m drying (an underlined figure, so 1.2 m above chart datum). Your yacht draws 1.6 m. You want a clearance of at least 0.5 m below the keel in a slight swell.

1. Required water depth: 1.6 + 0.5 = 2.1 m.
2. Required height of tide: the bar dries 1.2 m, so you need 1.2 + 2.1 = 3.3 m of tide to cover it to 2.1 m.
3. The tide tables show that the height of tide first reaches 3.3 m at 1840, and falls below 3.3 m again at 0105. This is the window in which you may cross, ignoring any swell.
4. Swell makes the bar breaking; reduce the window and remember that the lowest part of a wave trough can be well below the mean depth.

If you are early, you wait outside in deep water; if you are late, you cannot cross. Write the window on the plan.

Cross-stream and crabbing angle

A stream running across the entrance sets the boat sideways. If you steer straight at the entrance you will follow a curved path, ending up down-tide of where you intended. Instead, steer a heading that offsets the stream so that the ground track is the leading line.

Example. The leading line bears 320 degrees M. The stream sets across the line at 2 knots, and your speed through the water is 5 knots. For simplicity the stream is at right angles to the line, setting 050 degrees M (to the right of the line). The sine of the correction angle is 2 divided by 5 = 0.4, giving about 24 degrees. The stream is setting you to the right of the line, so you must head into it, to the left of the line: steer 320 minus 24 = 296 degrees M. Your speed along the line will be about the square root of (25 minus 4), which is 4.6 knots.

In practice, nobody steers a compass heading in an entrance. Hold the leading marks in line, and the compass heading you finish up on is your check against the plan.

Reaction time. At 5 knots the boat covers 0.083 miles a minute (about 150 m), and a 2 knot cross-stream sets it sideways about 60 m a minute. If you take your eyes off the transit for two minutes, you can be 120 m off the line, which is more than the width of many small harbour channels. This is why the plan has a helm, a lookout on the marks, and someone else calling depth.

Entering with the stream or against it

• Against the stream: the boat has slower ground speed and more time to think and manoeuvre, and rudder effect is maintained. Preferred for entering an unfamiliar harbour.
• With the stream: ground speed is higher and steerage is poorer, and if something goes wrong you have less time. Avoid unless there is no choice.
• Wind against tide: in an entrance with a strong ebb and onshore wind, the sea may be steep and breaking. If the stream is over about 3 knots and the wind is over Force 5 against it, do not enter; use the contingency plan.

Buoyage in the Approach

The approach to nearly every harbour uses IALA Region A buoyage. Know exactly what you will see and what each mark means before arrival.

The direction of buoyage matters. In Region A you keep red to port when entering a harbour from seaward. In a river or estuary the chart shows the direction of buoyage with a magenta arrow; this is not always from seaward, so check it. Cardinal marks are more reliable than lateral marks when you have a choice, because they give the side of the danger on which to pass.

Buoys swing on their chains and can be moved or off station in a storm. Treat buoys as a guide to where the channel is, not as a fixing mark, and cross-check the position from fixed marks such as beacons, churches and lights.

Using a Pilot Book

The pilot book or almanac harbour entry is the starting point for a plan, but it is never the whole plan.

• Read the entry through twice. The first reading is for the picture, the second for the details: tidal restrictions, hazards, leading lines, speed limits and VHF.
• Note the date of publication and check for corrections. Marks change, dredging moves the channel and new marinas appear.
• Look at the photograph or sketch and imagine the view from your approach. Draw it on the plan.
• Reconcile the pilot book and the chart. If they disagree, take the more cautious. Contact the harbour master by VHF or phone for local information.
• Never rely on the pilot book alone for depths. Use the chart with a tide correction, and ask for the latest dredged depth.

Lights and Night Pilotage

At night the shapes and colours of marks disappear and only lights remain. Lights are identified by their colour and their characteristic (the pattern of flashes) and period.

Sector lights

A sector light shows different colours over different arcs of bearing. Usually a narrow white sector marks the safe channel, with red on one side and green on the other. If you see white, you are in the safe sector; if the light turns red or green, you are moving out of it. The chart gives sector limits as bearings from seaward, towards the light.

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Check the chart for which colour lies on which side for your particular light — red to port and green to starboard is common for an inbound vessel in Region A, but not universal. Some sector lights use intensified or oscillating boundary sectors.

Night pilotage technique

• Protect your night vision: red lighting below and on deck, dimmed instruments, 20 to 30 minutes of dark adaptation; announce before switching on a white light.
• Identify every light with a stopwatch: count flashes in a group and time the full period. Compare with the chart description exactly.
• Remember that background lights (street lamps, cars, shore lights) can hide navigation lights. Identify lights from further out where possible.
• Unlit marks are a hazard: plan to pass them with margin, and use clearing lines from lit marks.
• Distances are hard to judge at night; rely on bearings, transits and the echo sounder.
• Do a first entry in daylight if you can, and plan night entries to well-lit harbours.

Abort Points, Point of No Return and Contingencies

Every plan needs a "what if". Decide in advance, calmly, at the chart table, at which points you will turn back and on what criteria.

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• Abort point: a position at which you assess conditions against criteria. Example criteria: "If I cannot identify the leading marks by the outer waypoint, I turn back"; "If visibility falls below half a mile, I anchor in the bay"; "If the engine fails, sail back out to the waiting area".
• Point of no return: in some entrances (narrow channels, over bars in onshore swell, strong following streams) there is a point after which turning round is more dangerous than continuing. Know where it is, and be certain before you pass it.
• Why decide in advance: decisions made under pressure, in the dark, with tired crew, are poor. Pre-briefed criteria remove the debate and let the crew act calmly.

Contingency anchorages and ports of refuge

If entry becomes impossible — wind against tide in the entrance, fog, an engine failure, a closed port — you need somewhere else to go.

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Note in the plan: the position, depth at all states of tide, holding ground (sand and mud are good; rock and weed poor), shelter from the forecast wind, and the approach bearing. Have at least one option sheltered from each likely wind direction.

VHF and Harbour Communications

Most commercial and many leisure harbours have a harbour authority or VTS (vessel traffic service) operating on a published VHF channel. Some require all vessels to call; many only require vessels over a certain length, but leisure craft should still monitor.

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Good practice:

1. Note in the plan the working channel(s), any reporting points, and traffic signal meanings.
2. Switch to and monitor the harbour channel well before the entrance (dual watch with Channel 16 if possible). Listen to traffic movements — ferries and ships leaving are announced.
3. Call at the point specified (or on approach), stating the vessel name, position, intention and length if asked. For example: "Dartmouth Harbour, Dartmouth Harbour, this is yacht Seabird, Seabird. Approaching the entrance, request a berth for one night, 10 metres, over."
4. Obey port traffic signals (see the table below). Local variations exist, so look up the meaning for your port in the almanac.
5. Keep to the starboard side of narrow channels (Rule 9) and do not impede large vessels which can navigate only within the channel.

International Port Traffic Signals (IPTS)

Many ports, locks and bridges use the IPTS, which every almanac prints on its reference pages. The main message is always three lights in a vertical column, which is how you tell a traffic signal from navigation lights. Red means "do not proceed", green means "proceed, subject to the conditions stipulated", and red and green are never shown together. The serious emergency signal flashes at least 60 times a minute; every other signal is fixed or slow occulting.

Some signals are shown to all vessels at once; others are directional, shown only to vessels entering or only to vessels leaving. Where the exemption signal 2a is shown, a yacht that can keep outside the dredged channel may go in while a ferry waits; where the plain signal 2 is shown, everybody waits.

Briefing the Crew

Pilotage is a team activity. A clear briefing before the approach makes each person useful.

Give crew the plan and the abort criteria before you reach the first mark. Tell them that anyone can call "stop" if they are uncertain or see something not on the plan. In the first entry to an unknown harbour, reduce speed so that there is time to respond: 4 knots in a crowded entrance is better than 6 and a collision.

Electronic Aids in Pilotage

Chartplotters, AIS and radar are good additions to a plan but must not replace it.

• Chartplotter. Use at the largest scale and compare against what you can see. Mark the plan's waypoints and the abort positions on the plotter. Note that a small error in the plotter, a datum difference or an old chart can place you metres from the real position, which in a channel 40 m wide matters.
• AIS. Shows large vessels in the entrance, their speed and destination. Use it to avoid meeting a ferry in a narrow section.
• Radar. Valuable in fog: use a range and bearing on a charted mark and the radar overlay on the plotter. Do not enter a restricted-visibility entrance unless you can fix by visual marks or radar and the sounder together.
• Echo sounder. The most useful electronic aid in pilotage. Keep the alarm set.

The principle is that the visual plan comes first. Electronic aids confirm the plan or warn you that something is wrong.

Pilotage Without Local Knowledge: A Checklist

Before leaving the last safe position:

1. State of tide and time window: confirmed.
2. Wind and sea: acceptable for the entrance, with the abort option.
3. Plan on deck: legs, headings, lights, clearing lines, abort points and VHF.
4. Crew briefed, with roles and calls.
5. Engine running and in neutral, ready; sails reduced or stowed so as not to obstruct the helm view.
6. Fenders and warps ready, depending on the berthing plan.
7. Echo sounder on, alarm set; handheld VHF and flares to hand; lifejackets worn.
8. Harbour contacted, if required, and the berth confirmed.

Worked Example — Planning an Entry

You plan to enter a small Devon harbour at 2130 on a summer evening (sunset 2115). The entrance runs north-west between rocks, with a leading line on 320 degrees M and a sector light.

1. Approach: from the waypoint 1.5 miles south-east of the entrance, steer for the entrance light. Expect to see the Fl G 5s starboard-hand beacon and the Fl(2) R 10s port-hand beacon.
2. Leading line: front light Oc 3s, rear light Oc 3s, in line on 320 degrees M. With the tide setting east across the entrance at 1 knot, expect to head about 310 degrees M to hold the line.
3. Clearing line: a rocky ledge lies 2 cables to the east of the line. Clearing bearing: "Keep the castle light bearing more than 300 degrees M." Check by hand-bearing compass every two minutes.
4. Depths: charted depth on the line is 4.0 m minimum; height of tide at 2130 is 2.1 m; expect at least 6.1 m. Shallow alarm set to 4.0 m.
5. Turn point: when the inner Fl G beacon is abeam to starboard, turn to port onto 270 degrees M for the marina.
6. Abort: if you cannot positively identify both leading lights by the outer waypoint, or if visibility is under 1 mile, do not enter: anchor in the sheltered bay to the west (5 m, sand, sheltered from SW to N).
7. VHF: monitor Channel 14 from the waypoint; call the harbour at the entrance.

Written up, this fits on one side of a card and can be read in seconds by the helm or navigator.

Worked Example: A Night Entry With a Sector Light

You are approaching a small harbour at 0045 in light airs, using the engine. The chart shows a light on the end of the breakwater, Fl(2) WRG 10s, with the white sector from 325 to 335 degrees T (bearings from seaward), red on the port side and green on the starboard side as you enter. Variation is 2 degrees W. The harbour entrance is 200 m wide.

1. Light identification. From 5 miles off you see a flashing white light. Using the stopwatch, you record two flashes in a group, with a period of 10 seconds. This matches Fl(2) 10s. You do not enter until you have timed it for at least two full periods and it matches.
2. Sector. The white sector, 325 to 335 degrees T, equals 327 to 337 degrees M (add the 2 degrees W variation to convert True to Magnetic). Steer to keep the light white. If the light shows red you are on the port side of the safe water: alter to starboard until it turns white. If it shows green, alter to port.
3. Cross-check. The echo sounder shows 7.5 m; the height of tide is 2.0 m, so the charted depth is about 5.5 m, which matches the chart at the entrance.
4. Speed. Reduce speed to 3.5 knots at 0.5 miles, so that the crew can see and call depths.
5. Hold the white. Narrow your focus to keeping the light white. If it turns red or green, alter back towards the middle of the white at once. Do not aim to sit on the sector edge: stay in the middle of the white.
6. Inside the entrance. The marina lights and street lighting appear. Check the next marks against the plan: a Fl R 5s port-hand beacon at the end of the pier. Call the harbour on Channel 12 at 0.3 miles.

At each step you are checking the plan, not discovering the harbour.

Exam Tips

• Be ready to produce a pilotage plan for a harbour unseen, from the almanac and chart, in a set time.
• Quote clearing bearings with the correct "more than" or "less than", and show the working on the chart.
• Know all the light abbreviations and the cardinal mark patterns from memory.
• When asked "what if", answer with the abort point you chose in advance, not a decision made on the spot.
• Show on your plan how you will identify marks, not just where they are.

Common Mistakes

Over-detailed plans

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If you have to read a paragraph while manoeuvring, you are not looking outside. Keep the plan in short notes, big writing, with headings and bearings prominent.

Misidentifying lights

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Fl(2) 10s, Fl(2) 15s and Fl(3) 10s look alike at a glance. Count and time each light with a stopwatch, over at least two full periods, and check against the chart before you rely on it. If a light you expect does not appear, stop and work out why — do not assume the nearest flashing light is the one you want.

Ignoring the tidal stream

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A cross-stream sets you towards dangers even when you are steering exactly at a mark. Check the stream direction for every leg; give more room to dangers down-tide of you, use transits to see the set immediately, and where you can, approach so that the stream would carry you away from hazards if anything goes wrong. Entering against the stream also gives you better steerage and a slower speed over the ground.

Other mistakes

• Relying solely on the chartplotter in an entrance: plotters can be a few metres to tens of metres out, and charts of small harbours are not always accurately surveyed.
• Not briefing the crew: tell them what to look for and give them jobs (lookout for a specific mark, depth calls, bearings).
• Arriving at the wrong state of tide or in wind-against-tide conditions.
• Forgetting traffic: large vessels in narrow channels cannot stop or turn.

Summary

• Pilotage is navigating by eye close to danger; it is done with a prepared plan, not at the chart table.
• Keep the plan on one page in short notes: legs, headings, what to see, turn points, clearing lines, depths, lights, abort criteria and VHF.
• Transits and leading lines give exact ground tracks with no compass error.
• Clearing bearings keep you on the safe side of a danger with a single compass check.
• Pre-calculate echo sounder readings and use depths to confirm the plan.
• At night, identify every light by colour, characteristic and period, using a stopwatch; use sector lights to stay in the safe white sector.
• Decide abort points and contingency anchorages in advance.
• Monitor and call harbour VHF channels and obey traffic signals.

Check Your Understanding

1. Why must pilotage be planned in advance rather than worked out by plotting fixes as you go?

Answer: Close to danger, events happen in a minute or two — too quickly to go below and plot. The thinking must be done in advance so that on deck you only need quick visual checks.

1. The front leading mark appears to the right of the rear mark. Which way are you off the line, and which way do you turn?

Answer: You are to the left of the line; turn right (towards the front mark) until they are in line again.

1. A clearing bearing reads "keep the spire bearing more than 270 degrees M". You take a bearing of 265 degrees M. What does it mean?

Answer: You are on the dangerous side of the clearing line. Alter immediately towards safe water until the bearing is again more than 270 degrees M.

1. What is the difference between a Fl and an Oc light?

Answer: In a flashing light the period of light is shorter than the darkness; in an occulting light the period of light is longer than the darkness.

1. You are approaching a sector light and it changes from white to red. What does this tell you?

Answer: You have moved out of the safe white sector into the red sector — check the chart to see which side of the channel that is, and alter back into white.

1. What is a point of no return and why should it be in the plan?

Answer: The position beyond which turning back would be more dangerous than continuing (e.g. in a narrow entrance or over a bar). You must know where it is so that you make the go/no-go decision before reaching it.

1. Charted depth on your track is 3.5 m and the height of tide will be 1.8 m. Your echo sounder displays depth below the surface. What should it read, and what do you do if it reads 2.5 m?

Answer: About 5.3 m. A reading of 2.5 m means you are not where you think — slow down or stop, and turn back towards known deep water before re-checking your position.

1. Name four things to record about a contingency anchorage.

Answer: Any four of: position, depth at all states of tide, holding ground, shelter from forecast winds, approach bearing and hazards.

1. What should you do on VHF before entering a busy harbour?

Answer: Monitor the harbour working channel well before entry, listen for traffic movements, and call the harbour at the designated point if required.

1. A bar dries 0.8 m and your yacht draws 1.5 m. You want 0.5 m clearance below the keel. What height of tide do you need to cross?

Answer: Required depth is 1.5 + 0.5 = 2.0 m, and the bar dries 0.8 m, so you need a height of tide of 0.8 + 2.0 = 2.8 m at the time you cross.

1. A leading line bears 270 degrees M. A 1.5 knot stream sets at right angles to it, to the south. Your speed through the water is 5 knots. Roughly what heading holds the line?

Answer: The sine of the correction angle is 1.5 divided by 5 = 0.3, giving about 17 degrees. The stream sets you south, so head into it, to the north of the line: about 287 degrees M. In practice, hold the marks in line and note the heading.

1. Your sector light shows red as you approach and the plan says the white sector is the safe channel. What do you do, and what should you not do?

Answer: You are outside the safe white sector on the red side: check the chart for which side that is and alter towards the white. Do not continue on the red, and do not aim to sit on the edge of the sector, which should be avoided because the colour boundary is not sharp.