Lesson 32 of 40 · Module 5 — Planning and pilotage

Passage planning

Putting it all together: tides, weather, hazards, ports of refuge and timings.

Coastal Skipper30 minVideo · Notes · Interactive · Exercises

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0:00 / 5:12Chapter 1 of 9: Plan before you go

Transcript

A passage plan is the thinking you do at the chart table before you leave, so that the decisions at sea are easy. In this lesson we plan a passage on the practice chart, from Port Kerran, round the island, to the anchorage in Kerran Roads. There are two ways round, and the plan must decide which, when to leave, and what to do if things change.
Every plan answers the same questions. What will the tide be doing, up and down and sideways, and what will the weather do? Where are the dangers, and which route and waypoints keep you clear of them? How long will each leg take, and when will you arrive? Where could you shelter if you had to, and what will you do if something goes wrong? And are the crew and the boat ready for it?
First, which way round? Going west, past Kerran Head, is about a mile shorter. But it passes Mew Rock, the wreck and Head Ledge, and in today’s south-westerly its fair stream, the ebb, would run against the wind. Going east, round Gull Point, there is one well-marked danger, The Teeth, and the fair stream there is the flood, running with the wind. So the plan goes east.
Gull Point is the tidal gate: the stream runs hardest off the headland, so when you pass it matters most. Leave waypoint one at ten hundred and you pass the point around high water, with one point six knots from diamond B carrying you round. Leave at fifteen hundred and the ebb has turned: one point five knots against you, and against the wind, cutting your speed over the ground to under four knots. The stream at B stays fair until about fourteen twenty-two, and turns foul at about fifteen twenty-two. So we plan to leave waypoint one at eleven thirty, passing the point with wind and stream together.
Now break the route into legs between waypoints. Waypoint one is at the seaward end of the leading line. Waypoint two is south-east of the East Teeth buoy, and waypoint three north-east of Gull Point, both well outside The Teeth. Waypoint four is just north of the Kerran Roads anchorage. Measure each leg: zero five two degrees for six point five miles, then due north for two point eight, then two eight eight degrees for five point nine. That is fifteen point two miles, about three hours at five knots.
For each leg, work out the course to steer, just as in lesson twenty-nine. Leg two runs due north, about an hour after high water, when diamond B gives zero five zero degrees at one point four knots. A one-hour triangle would run off the top of this chart, so here it is drawn at half size: half an hour of stream, then half an hour’s boat speed to cut the track. Scaling both lines alike keeps the angles, so the water track is still three four eight degrees true, and the cut is two point nine miles along the track in half an hour: a speed over the ground of five point eight knots. Add three degrees of westerly variation for three five one degrees magnetic, and the deviation card gives three five three degrees by the steering compass.
At the far end, check the depth where you plan to anchor. Kerran Roads is a secondary port: high water there is at twelve zero four, four point four metres, and low water at eighteen ten, zero point nine metres. Anchored at about fourteen fifty, the height of tide is about three point zero metres, so over the six point five metre sounding there is about nine point five metres. At low water this evening that falls to seven point four metres, still five point six metres under our one point eight metre keel.
A good plan also says what you will do if things change. Port Kerran, behind you, is the bolt hole: the island shelters it from the north, while Kerran Roads is open to northerly winds. Set a decision point: if you are not at waypoint two by about fourteen twenty-two, the fair stream at Gull Point has gone, so turn back rather than meet the ebb off the point. And decide now what you would do about a failed engine, fog or a seasick crew, before you need to.
Once under way, keep checking the plan. Fix your position at least hourly, and compare it with where the plan says you should be. At twelve thirty our fix is almost a mile short of the planned position: the wind has dropped, and we have made good only four point nine knots. At that speed we reach waypoint two at about twelve forty-nine, not twelve thirty-eight: still well before the fourteen twenty-two decision time, so the plan stands. If the numbers ever say you will miss the gate, change the plan early, while you still have choices.

In this lesson you will learn

Explain what a passage plan is for and list what goes into one
Use tide tables and tidal diamonds to find a tidal gate and choose a departure time that carries a fair stream past a headland
Choose waypoints and work out each leg’s track, distance, course to steer, time and ETA
Check the depth at the destination, and identify hazards, ports of refuge and contingency plans
Monitor a passage with fixes and EPs and decide when to change the plan

What a passage plan is for

You now have every tool a coastal navigator needs: chart work, the compass, EPs and fixes, buoyage and lights, tidal heights and streams, the course to steer and leeway. A passage plan puts them together before you leave, at the chart table, where you have time to think. It answers three questions: can we go (are the boat, crew and weather up to it), how and when do we go (route, timing, tides), and what do we do if things change.

Professional mariners often describe it in four stages: appraisal (gather the information), planning (make the plan), execution (carry it out) and monitoring (check progress against it). As Lesson 15 noted, the UK Maritime and Coastguard Agency’s guidance is that the voyage-planning requirement in Chapter V of SOLAS applies to pleasure craft as well as ships, with the amount of planning depending on the boat and the passage. For a day sail the plan can fit on one card; what matters is that the thinking has been done.

Decide in harbour, when it is calm and you have time. At sea, you then only have to check and choose.

What goes into a plan

Part	What you need to know	Where from
Objective and constraints	Where, when you must arrive, daylight, crew experience, boat speed and draught	You and your crew
Charts and pilot information	Dangers, marks, harbour and anchorage notes, entry restrictions	Charts (largest scale for harbours), almanac, pilot book
Tidal heights	Enough water to leave, to cross shallows and to arrive	Tide tables, secondary port differences, tidal curve
Tidal streams and gates	When the stream is fair or foul, especially off headlands	Tidal diamonds, stream atlas
Weather	Wind strength and direction, sea state, visibility, how it may change	Official marine forecasts, re-checked before you go
Hazards and clearing lines	What to avoid and how you will know you are clear	Chart; clearing bearings (Lesson 13)
Route, waypoints and legs	Track, distance, course to steer and time for each leg	Chart work (Lessons 5, 6 and 29)
Timings and ETAs	When to slip, when you pass each waypoint, when you arrive	Your leg times
Ports of refuge and contingencies	Where to shelter, decision points, plan B	Chart, pilot book, forecast
Crew, boat, fuel and safety	Briefing, checks, fuel and water, safety kit; who ashore knows your plan	Your checklists

The worked passage: which way round?

On Sat 12 Jun 2027 we want to take the course yacht (draught 1.8 m, 5 kn through the water, a crew of three, one of them new to sailing) from Port Kerran to the Kerran Roads anchorage on the north side of the island, and anchor there in daylight. The forecast is south-westerly force 3 to 4 with good visibility. Kerran Roads is sheltered from southerly winds, so it suits the forecast.

Two ways round. East (teal) round Gull Point: 15.2 M from WP1. West (brown, dashed) round Kerran Head: 14.3 M.

	West, round Kerran Head	East, round Gull Point
Distance from WP1	14.3 M	15.2 M
Dangers	Mew Rock (dries 1.2 m), the wreck and Head Ledge; a straight line out of the bay passes within 2.8 cables of Mew Rock, so it needs a dog-leg	The Teeth, guarded by two cardinal buoys; we pass 0.9 M off
Fair stream at the headland	The west-going ebb: against the south-westerly wind	The east-going flood: with the wind

West is about a mile shorter, but it has more dangers and, today, wind against tide off its headland. We go east.

Tides: heights, streams and the tidal gate

First the heights. Converted to BST, Port Kerran has LW 0541 (1.1 m), HW 1152 (4.6 m) and LW 1802 (0.9 m): a range of about 3.7 m, roughly halfway between neaps and springs. The way out of Port Kerran down the leading line has more than 5 m at chart datum all the way (Lesson 31), so the height of tide doesn’t limit our departure. For the arrival, Kerran Roads (Lesson 27) has HW 1204 (4.4 m) and LW 1810 (0.9 m).

Port Kerran — times UT (add 1 hour for BST), heights in metres above chart datum
Day	Time	m	HW/LW
Sat 12 Jun	0441	1.1	LW
	1052	4.6	HW
	1702	0.9	LW
	2312	4.8	HW

Now the streams. A tidal gate is a place you can only pass comfortably at certain states of the tide — usually a headland, where the stream runs hardest. Ours is Gull Point, with diamond B just off it. A stream is fair when it helps you along your track, foul when it is against you, and slack when it is weak and turning. Reading diamond B for each tidal hour of the day (Lesson 28), for leg 2, heading north past the point:

Tidal streams referred to HW Port Kerran — direction °T, rates in knots at springs and neaps
Hours	B49°48.3'N 004°03.2'W
Hours	DirSpNp
6 before	2301.60.8
5 before	2351.00.5
4 before	3000.30.1
3 before	0401.00.5
2 before	0451.90.9
1 before	0502.41.2
HW	0502.21.1
1 after	0501.80.9
2 after	0551.10.5
3 after	1200.30.1
4 after	2201.10.5
5 after	2252.01.0
6 after	2302.31.1

Tidal hour (BST)	Row	Stream at B	For leg 2 (north)
0722–0822	HW−4	300°T 0.2 kn	slack
0822–0922	HW−3	040°T 0.7 kn	fair
0922–1022	HW−2	045°T 1.4 kn	fair
1022–1122	HW−1	050°T 1.8 kn	fair
1122–1222	HW	050°T 1.7 kn	fair
1222–1322	HW+1	050°T 1.4 kn	fair
1322–1422	HW+2	055°T 0.8 kn	fair
1422–1522	HW+3	120°T 0.2 kn	slack
1522–1622	HW+4	220°T 0.8 kn	foul + wind against tide
1622–1722	HW+5	225°T 1.5 kn	foul + wind against tide

The gate is open (fair) until about 1422, slack until about 1522, then shut: the ebb sets south-west, against us and against the wind.

Worked example

Two departures compared at the gate

1Leave WP1 at 1000: leg 1 takes 1 h 07 min, so we are on leg 2 about 1123 (HW). B: 050°T 1.6 kn — fair. Vector triangle: SOG 5.9 kn, leg 2 takes 29 min.
2Leave at 1500: leg 1 is slower (1 h 26 min), and we are on leg 2 about 1643 (HW+5). B: 225°T 1.5 kn — foul, and against the wind. SOG 3.8 kn, leg 2 takes 44 min.
3Whole passage: 3 h 03 min against 3 h 10 min. Going round an island you meet a foul stream somewhere whichever time you choose, so total times differ by less than you might expect — the big difference is the sea state off the point.

Pass Gull Point while B is fair: we plan to leave WP1 at 1130 BST (2 h 55 min), with an hour in hand before the gate closes.

Leave WP1	Off Gull Point	Stream at B	SOG past the point	WP1 → WP4
0900	1025	050°T 1.8 kn	6.0 kn	3 h 04 min
1000	1123	050°T 1.6 kn	5.9 kn	3 h 03 min
1100	1224	050°T 1.4 kn	5.8 kn	3 h 01 min
1200	1326	055°T 0.8 kn	5.4 kn	2 h 58 min
1300	1429	120°T 0.2 kn	4.9 kn	2 h 52 min
1400	1535	220°T 0.8 kn	4.4 kn	2 h 58 min
1500	1643	225°T 1.5 kn	3.8 kn	3 h 10 min
1600	1749	230°T 1.8 kn	3.6 kn	3 h 23 min

InteractiveDeparture time and the tidal gate

Slide the departure time from WP1. Watch the stream at B when you reach Gull Point, the SOG past the point, each leg’s stream and course to steer, and the total passage time. Try other days and boat speeds too.

Day (June 2027)

Speed through the water

Leave WP1 at 1130 BST

Off Gull Point about 1254 (HW+1): diamond B sets 050°T 1.4 kn — fair (with you) for the leg north. Speed over the ground past the point: 5.8 kn.

Passage WP1→WP4: 2 h 55 min, arriving about 1425 BST.

Leg	Start	Track, distance	Stream (mid-leg)	CTS	SOG	Time
WP1→WP2	1130	052°T 6.5 M	A HW: 070°T 0.8 kn	049°T052°M · 051°C	5.8 kn	1 h 08 min
WP2→WP3	1238	000°T 2.8 M	B HW+1: 050°T 1.4 kn	348°T351°M · 353°C	5.8 kn	29 min
WP3→WP4	1307	288°T 5.9 M	D HW+2: 100°T 0.5 kn	287°T290°M · 294°C	4.5 kn	1 h 18 min

Each leg uses its nearest diamond (A, B, then D) for the hour in the middle of the leg, found from a first guess at 5 kn — a planning estimate, not a precise prediction.

With the south-westerly force 3 to 4 forecast, why is 1500 a poor time to leave WP1, even though the whole passage takes only about 7 min longer than leaving at 1000?

Waypoints, legs and courses to steer

Waypoints mark the ends of the legs. Put them in clear water, a safe distance from dangers and marks — never on a mark, or you may hit it — and somewhere you can identify. Our route uses four:

Waypoint	Position	Where
WP1	49°42.6'N 004°11.5'W	Seaward end of the leading line, north of Kerran Approach buoy
WP2	49°46.6'N 004°03.6'W	South-east of East Teeth buoy, well outside The Teeth
WP3	49°49.4'N 004°03.6'W	North-east of Gull Point, well north of North Teeth buoy
WP4	49°51.2'N 004°12.3'W	North of the anchorage: from here, pilot in by eye and echo sounder

From the harbour, the pilotage plan (Lesson 31) takes us 2.7 M down the leading line to WP1, so we slip at about 1055. For each leg, measure the track and distance, then work out the stream, course to steer and speed over the ground:

leg time = distance ÷ SOG

Use the stream for the middle of the leg, from a first guess at boat speed. For legs of an hour or so this is a fair planning estimate; Lesson 36 combines several hours of stream.

Leg	Track, distance	Mid-leg stream	CTS	SOG	Time	ETA
WP1→WP2	052°T 6.5 M	A HW: 070°T 0.8 kn	049°T 052°M	5.8 kn	1 h 08 min	1238
WP2→WP3	000°T 2.8 M	B HW+1: 050°T 1.4 kn	348°T 351°M	5.8 kn	29 min	1307
WP3→WP4	288°T 5.9 M	D HW+2: 100°T 0.5 kn	287°T 290°M	4.5 kn	1 h 18 min	1425

Worked example

Course to steer for leg 2, past Gull Point

1We reach WP2 at 1238. A first guess at 5 kn gives 34 min for the 2.8 M leg, so its middle is about 1254: 1 h 02 min after HW (1152 BST), the row HW+1.
2B, HW+1: 050°T, springs 1.8, neaps 0.9. Range 4.6 − 0.9 = 3.7 m; fraction (3.7 − 2.4) ÷ 2.4 = 0.54; rate 0.9 + (1.8 − 0.9) × 0.54 = 1.39, about 1.4 kn.
3Vector triangle (Lesson 29): ground track 000°T; from WP2 lay off one hour of stream, 050°T 1.4 M; from its end swing a 5 M arc to cut the track.
4Water track = course to steer 348°T; the cut is 5.78 M along the track, so SOG 5.8 kn and the leg takes 29 min.
5Wind on the port quarter: leeway is small on this point of sailing, so we ignore it for planning. Variation 2°44'W in 2027, 3°W for chart work: 348°T → 351°M. Deviation for a ship’s head near 353°C: 2.3°W (from the card) → 353°C.

Leg 2: steer 353°C (348°T), SOG 5.8 kn, WP3 at 1307 BST

Leg 2’s triangle, drawn here at half size because a one-hour triangle would run off the top of the chart: half an hour of stream, 0.7 M (three arrows), and half an hour’s boat speed, a 2.5 M water track (one arrow), cutting the ground track (two arrows) 2.9 M from WP2. Both lines are scaled to the same time, so the angles — and the course to steer — are the same as in the one-hour triangle; double the 2.9 M for the SOG, 5.8 kn. Never mix times in one triangle (Lesson 29).

InteractiveRoute builder

Choose a waypoint and tap the chart to move it, or try the presets. The legs table and a simple safety check update as you go. Can you find a shorter route that still passes the check?

Tap the chart to plot a positionZoom with + / −, drag to pan

Move:

Choose a waypoint, then tap the chart where you want it (or nudge it a cable at a time with the arrows).

Leg	Track	Distance	At 5 kn
WP1→WP2	052°T	6.5 M	1 h 18 min
WP2→WP3	000°T	2.8 M	34 min
WP3→WP4	288°T	5.9 M	1 h 11 min
Total		15.2 M	3 h 02 min

WP1 49°42.6'N 004°11.5'W
WP2 49°46.6'N 004°03.6'W
WP3 49°49.4'N 004°03.6'W
WP4 49°51.2'N 004°12.3'W

Safety check: no warnings. Every leg is in water deeper than the draught plus 2 m at chart datum, at least 3.0 cables from The Teeth, Head Ledge, Mew Rock and the wreck, and clear of every buoy.

A rough check for practice only. It looks at depths along each leg and a 3.0-cable margin — your margin is the skipper’s choice, and more is wise in poor visibility or with the stream setting you towards a danger.

Arrival: enough water at the anchorage

Worked example

Depth near the 6.5 m sounding in Kerran Roads

1WP4 at 1425; allow about 20 minutes to pick a spot and anchor: about 1450 BST.
2That is 2 h 46 min after HW Kerran Roads (1204). Range 4.4 − 0.9 = 3.5 m; the Port Kerran curve gives a factor of 0.60.
3Height of tide = 0.9 + 0.60 × 3.5 = 3.0 m. Depth = 6.5 + 3.0 = 9.5 m.
4At LW 1810: 6.5 + 0.9 = 7.4 m; under the keel 7.4 − 1.8 = 5.6 m. Next morning’s LW (0632, 0.8 m) leaves 7.3 m.

Anchor in about 9.5 m on arrival; never less than 7.3 m overnight

Hazards and clearing lines

Hazard	What it is	How the plan stays clear
Mew Rock	Isolated danger mark on a rock that dries 1.2 m	Leave the bay down the leading line, steering 180°T (183°M) with the lights in line astern, to WP1; the route then heads east, 2.7 M from it at the closest.
Brennan Bank	South cardinal on Brennan Bank, least depth 2.1 m	Leg 1 passes 2.8 M north-west of the south cardinal buoy.
The Teeth	Rocks awash off Gull Point (East and North Teeth buoys)	Pass east of East Teeth buoy and north of North Teeth buoy; WP2 and WP3 are outside both. Closest approach 0.9 M.
Kerran Roads foreshore	Shoals and dries towards the coast	From WP4, approach slowly, watching the echo sounder; anchor near the 6.5 m sounding.

Ports of refuge and plan B

A port of refuge (or bolt hole) is somewhere you can shelter if the weather, the boat or the crew let you down. For each one, the plan notes when you can get in (state of tide, at night, in strong onshore winds). On this chart there are two:

Port Kerran — behind us; the island shelters it from the north, and its lit leading line works at night.
Kerran Roads — our destination: sheltered from southerly winds, but open to the north.

Then decide, in advance, what would make you change the plan:

Decision point: at WP2 by 1422 BST, when the fair stream at Gull Point ends. Later than that, turn back.
Weather: a northerly, or more than force 5, means Port Kerran rather than Kerran Roads.
Engine failure: sail on if the wind allows; know where you could anchor clear of dangers.
Fog: stay outside the buoys, keep a careful plot with GPS and the echo sounder, and consider turning back.
Seasick or injured crew: Port Kerran is the nearest shelter for most of the passage.

Weather, crew and boat

Get the latest official marine forecast before you slip and again during the passage; Lesson 38 covers forecasts and how weather shapes a plan. Brief the crew on the plan, lifejackets, man-overboard drill, the VHF and where the safety kit is. Check the engine, and carry fuel for the whole passage under engine with a good reserve, plus water and charged batteries. Make sure the navigation lights work, in case you are late.

Writing it down

The written plan is short enough to keep at the chart table and to brief the crew from. Build ours:

InteractiveBuild the passage plan

Add each section to the plan card. Two sections ask you to make a decision first: try the other answers too.

0 of 12 sections in the plan

1Objective and constraints
2Charts and pilot information
3Tidal heights
4Which way round
Which way round the island?
5Tidal streams and the gate
When should you leave WP1?
6Weather
7Waypoints and legs
8Hazards and clearing lines
9Ports of refuge (bolt holes)
10Contingencies and decision points
11Crew, boat, fuel and safety
12Tell someone ashore

Passage plan · Port Kerran → Kerran Roads

Objective and constraints: —
Charts and pilot information: —
Tidal heights: —
Which way round: —
Tidal streams and the gate: —
Weather: —
Waypoints and legs: —
Hazards and clearing lines: —
Ports of refuge (bolt holes): —
Contingencies and decision points: —
Crew, boat, fuel and safety: —
Tell someone ashore: —

Monitoring the plan under way

A plan is a prediction. Fix your position at least every hour (more often near dangers), plot an EP between fixes, log it, and compare it with where the plan says you should be. Are you ahead or behind? On track, or being set off it? Is the stream or the wind what you expected?

Worked example

The 1230 fix

1Planned position at 1230: 5.8 M along leg 1. Our fix is only 4.9 M along: 0.9 M short. The wind has dropped.
2Made good: 4.9 M in 1 h 00 min = 4.9 kn. WP2 is 1.6 M ahead: new ETA 1249, not 1238.
3Re-plan the rest at 4 kn through the water: leg 2 with B at 050°T 1.4 kn, WP4 about 1506.

WP2 at 1249 is well inside the 1422 decision time: the plan stands.

Leg 1: the planned 1230 position (teal) and the 1230 fix, 0.9 M behind it.

Change the plan when the facts change: the weather is worse than forecast, you will miss a tidal gate, the crew are tired or ill, or something breaks. Change it early, while you still have choices.

Plan the passage, sail the plan, and keep checking it — ready to change it before you have to.

Key terms

Passage plan: The plan for a passage, made before leaving: route, tides, weather, hazards, timings, refuges and contingencies.
Appraisal, planning, execution, monitoring: The four stages of passage planning used by professional mariners.
Tidal gate: A place, usually a headland, best passed at a particular state of the tide.
Fair / foul stream: A stream helping you along your track (fair) or against you (foul).
Slack water: The short period when the stream is weak and turning.
Waypoint: A chosen position marking the end of a leg — in clear water, never on a mark.
Leg: The stretch of a route between two waypoints, with its own track, distance and course to steer.
ETA: Estimated time of arrival, at a waypoint or the destination.
Port of refuge (bolt hole): A harbour or anchorage you could divert to for shelter.
Decision point: A place or time set in the plan at which you decide whether to carry on.
Wind against tide: Wind blowing against the stream: shorter, steeper seas, worst off headlands.

Exercises

Check your understanding. You get a second try at each question, then the worked answer. Score 70% or more to complete the lesson — your progress is saved in this browser.

Which of these does NOT belong in a passage plan?

Use the dividers to measure leg 1, from WP1 (49°42.6'N 004°11.5'W) to WP2 (49°46.6'N 004°03.6'W). How long is it, in miles?

Distance A→B: 1.20 MBearing A→B: 060°TDrag A and B, or Tab to them and use the arrow keysZoom with + / −, drag to pan

Measure the track of leg 3, from WP3 (49°49.4'N 004°03.6'W) to WP4 (49°51.2'N 004°12.3'W), in degrees true.

Distance A→B: 1.20 MBearing A→B: 240°TDrag A and B, or Tab to them and use the arrow keysZoom with + / −, drag to pan

The route from WP1 to WP4 is 15.2 M. For a first estimate, ignoring the stream, how many minutes does it take at 5 knots?

On Sat 12 Jun 2027 the stream at B (off Gull Point) is fair for the leg north until about 1422 BST, slack until 1522, then foul. The forecast is south-westerly 3 to 4. Leg 1 takes a little over an hour. Which departure from WP1 is best?

Leaving at 1500 instead, diamond B gives 225°T 1.5 kn on leg 2 (track 000°T). Your speed through the water is 5 kn. From the vector triangle, what is your speed over the ground?

On the planned departure you are on leg 2 (track 000°T) about 1254 BST, when diamond B gives 050°T 1.4 kn. At 5 kn through the water, what course should you steer, in degrees true?

You anchor in Kerran Roads near the 6.5 m sounding. LW Kerran Roads this evening is 1810 BST, 0.9 m. Your draught is 1.8 m. How much water will there be under the keel at LW?

Before you slip, the latest forecast changes to northerly 5 to 6. Kerran Roads is sheltered from southerly winds but open to the north. What is the sensible change to the plan?

At 1230 your fix is 0.9 M short of where the plan expected you. What should you do first?

0 of 10 answered · 0 correct

Passage planning practice

Five fresh questions each time: the stream at the Gull Point gate on a random day, fair or foul, a vector triangle for one of the legs, a leg time, and the depth at the anchorage at low water.