Training guides

Read the chart like a navigator

What every mark on the training charts means, how the tidal levels relate, and the step-by-step methods the planner computes for you. Symbols drawn to match this app’s charts; conventions follow the international standard. This is a training subset of the most-used chart symbols — not a substitute for the official Admiralty Chart 5011 / NP5011.

Tides

Tidal levels & datums

Everything on the chart is measured from chart datum (CD) — roughly the lowest the tide ever falls. Heights of tide are added to charted depths; drying heights stick up above CD and need the tide to cover them.

HAT: Highest astronomical tide — bridge clearances are measured above this.
MHWS / MHWN: Mean high water springs / neaps.
MLWN / MLWS: Mean low water neaps / springs.
CD: Chart datum — soundings and drying heights are referenced here.

Chart symbols

Depths & dangers

	Sounding	Depth below chart datum in metres and decimetres — 12.8 m here, at the position of the figures.
	Drying height	Underlined figure on green: dries 3.2 m ABOVE chart datum — covered only when the tide exceeds it.
	Depth contour	Joins points of equal depth; the training charts band white → blues as water shallows.
	Underwater rock	Dangerous to surface navigation; depth unknown unless figures are shown beside it.
	Submerged wreck	'Wk' in a dotted dangerline; a sounding beside it is the least depth over the wreck (4.6 m here).
	Swept wreck	Depth with a bar beneath: cleared to that depth by wire sweep — safe if you have the water.
	Obstruction	Danger whose exact nature is unknown or unspecified — treat with the same respect as a rock.
	Foul ground	Not a danger to navigation on passage, but never anchor or trawl here — old wreckage and debris below.
	Qualifiers	Position Approximate / Doubtful; Existence Doubtful; Sounding Doubtful — the chart telling you how much to trust it.
	Overfalls / tide rips	Rough, broken water where streams run hard over uneven bottom — time your passage for slack or fair stream.
	Tidal diamond	Lettered position with an hourly table of stream set and rate (neaps/springs), referenced to HW at the standard port.

Buoyage

IALA region A marks

Direction of buoyage on the training charts runs with the flood stream — into the sound or firth from seaward.

	Port-hand lateral	Red can — leave to PORT when entering with the flood. Light: red, any rhythm.
	Starboard-hand lateral	Green cone — leave to STARBOARD when entering. Light: green, any rhythm.
	North cardinal	Black over yellow, topmark ▲▲ — pass NORTH of it. Light: continuous quick white.
	South cardinal	Yellow over black, topmark ▼▼ — pass SOUTH of it. Light: 6 quick flashes + 1 long.
	Safe water mark	Red and white vertical stripes — navigable water all round; often the seaward landfall mark.
	Isolated danger	Black with red band(s), topmark ●● — danger beneath with navigable water around. Light: white, group flash 2.

Method

The two core workings

Course to steer

1Draw the ground track from departure point to destination.
2Find the hour’s stream from the nearest tidal diamond — interpolate the rate between neaps and springs using the day’s range.
3Plot the stream vector from your start point.
4From its end, swing one hour of boat speed to cut the track — that line is your course to steer.
5Distance made good along the track in the hour is your SOG; apply variation (and deviation) for the compass course.

Height of tide

1Look up HW and LW either side of your time at the standard port.
2Today’s range = HW − LW; compare with mean ranges to judge springs or neaps.
3Enter the tidal curve at your interval from HW and read the factor.
4Height = LW + factor × range. Add it to the charted depth (or subtract a drying height) and check against draught plus safety margin.

The planner shows each of these steps in the leg workings and the tidal curve — the point is to check them against your own paper plot, not to skip the plot.

Quick-reference cards

The tables worth printing in your head: light rhythms, day shapes, the sound-signal vocabulary, forecast terms, the knots, and both tidal methods as bare steps.

Lights

Light rhythms & notation

F	Fixed — steady
Fl	Flashing — more dark than light
Fl(3)	Group flashing — 3 together, then dark
LFl	Long flash (≥2 s)
Oc	Occulting — more light than dark
Iso	Isophase — equal light and dark
Q	Quick (~1/s)
VQ	Very quick

Fl(3)W.15s rhythm·colour·period 21m elevation above MHWS 24M nominal range

Shapes

Day shapes

● (forward)	At anchor
▼ cone point-down	Motor-sailing
● ●	Not under command
● ◆ ●	Restricted in ability to manoeuvre
▮ cylinder	Constrained by draught
▼▲ cones point-to-point	Fishing / trawling
◆ (both ends)	Tow over 200 m
● ● ●	AGROUND
Rigid flag A	Diving operations

Sound

Sound signals

Signal	Meaning
•	Altering to starboard
• •	Altering to port
• • •	Engines astern
• • • • •	Your intentions unclear — danger
▬ ▬ •	Narrow channel: overtake you to starboard?
▬ ▬ • •	…to port?
▬ • ▬ •	Agreement — go ahead
▬ (2 min, fog)	Power vessel making way
▬ ▬	Power vessel, stopped
▬ • •	Sail / fishing / NUC / RAM / tow in fog
• • • •	Pilot vessel on duty
bell 5 s/min	At anchor (+ gong aft if >100 m)
3 strokes·bell·3 strokes	Aground

Weather

Forecast terms

Timing

imminent <6 h · soon 6–12 h · later >12 h

Visibility

good >5 M · moderate 2–5 M · poor 1000 m–2 M · fog <1000 m

Warnings

gale = F8 or gusts 43 kn · severe gale = F9 or gusts 51 kn

Sea state (wave heights)

smooth <0.5 m · slight <1.25 · moderate <2.5 · rough <4 · very rough <6 · high <9 · very high <14 · phenomenal

Pressure tendency (per 3 h)

slowly <1.6 hPa · quickly 3.6–6 · very rapidly >6

Shipping Forecast running order: gale warnings → general synopsis → sea areas → coastal stations.

Ropework

The working knots

Bowline	Fixed loop — mooring lines, sheets to sails
Clove hitch	Fenders on a rail — quick, adjustable
Round turn & two half hitches	Rings and posts — releasable under load
Figure of eight	Stopper in a sheet’s tail
Rolling hitch	Grips along a loaded rope — frees jammed sheets
Sheet bend (double)	Joining two ropes, unequal sizes
Reef knot	Binding only — never as a bend

Tie them for real in the knot trainer.

Tides

The two tidal methods, step by step

Height at a time (curve)
HW time in the curve’s centre box; label the hours either side
Draw the range line: HW height (top scale) to LW height (bottom)
Enter at your time → up to the curve (springs or neaps)
Across to the range line → read the height. Reverse the path for time-at-a-height

Secondary port
Copy the standard port’s HW/LW times & heights — in the TABLE’S time zone
Interpolate each difference between its springs and neaps columns by the day’s range
Apply differences (mind the signs) → corrected times & heights
Use the standard port’s curve with the corrected figures · add the DST hour LAST

Chart symbol library

Organised by the INT 1 section letters used on the official Chart 5011, with the standard reference beside each symbol so you can cross-check against the real publication. All drawings original.

BPositions & compass3 symbols

Position approximate

B 7

PA — the charted position is not accurately determined or does not stay fixed.

Position doubtful

B 8

PD — reported in differing positions; treat the whole neighbourhood with suspicion.

Magnetic variation note

B 68

Printed variation with year and annual change, e.g. 4°30′W 2004 (9′E) — update it to today before converting.

HTides & streams5 symbols

	Flood stream arrow H 40	Feathered arrow — direction of the flood, often with mean spring rate alongside.
	Ebb stream arrow H 41	Plain (unfeathered) arrow — direction of the ebb.
	Overfalls, races H 44	Broken water where streams run hard over an uneven bottom — time for slack.
	Tidal diamond H 46	Lettered position keyed to the chart’s hourly stream table (set, spring and neap rates, referenced to HW at the standard port).
	Eddies H 45	Circling water downstream of points and obstructions.

IDepths5 symbols

	Sounding I 10	Depth below chart datum; the small subscript figure is decimetres — 12.8 m here, at the centre of the figures.
	Drying height I 15	Underlined figure: dries that height ABOVE chart datum — covered only when the tide exceeds it.
	Depth contour I 30	Line of equal depth; tints band from white (deep) through blues as water shallows.
	Dredged area I 21	Channel maintained to a stated depth, with the dredged depth and sometimes the survey year.
	ED / SD I 1–2	Existence Doubtful / Sounding Doubtful — surveyed long ago or reported once; give the benefit of the doubt to the danger.

JSeabed2 symbols

Holding letters

J 1–13

S sand · M mud · R rock · Sh shells · Wd weed — your anchor cares: sand and mud hold, rock and weed do not.

Kelp

J 13.2

Weed dense enough to chart — foul for anchors and propellers.

KRocks, wrecks, obstructions9 symbols

	Dangerline K 1	Dotted line drawing attention to a danger, or enclosing an area unsafe to navigate.
	Rock which covers K 11	Asterisk: covers and uncovers with the tide; a figure beside it is its drying height.
	Rock awash K 12	Cross with dots: awash at chart datum — exactly at the worst possible level.
	Underwater rock K 13	Plain cross: depth unknown, dangerous to surface navigation.
	Dangerous wreck K 28	“Wk” in a dotted dangerline — depth unknown, considered dangerous to surface vessels.
	Swept wreck K 27	Least depth cleared by wire sweep, shown with a bar under the figure — trustworthy if you have the water.
	Obstruction K 40	“Obstn” — something dangerous whose exact nature is unknown or unspecified.
	Foul ground K 31	Safe to sail over, never to anchor or trawl in — wreckage and debris on the bottom.
	Breakers K 17	Sea breaking over a shoal — visible warning of very shallow water.

NAreas & limits3 symbols

Anchorage

N 12

Recommended or designated anchoring area.

Anchoring prohibited

N 20

Anchor struck through — usually cables or pipelines beneath.

Restricted area

N 2

T-dashed magenta limit — entry or activity restricted; read the chart note.

PLights4 symbols

	Light P 1	Star with a magenta flare — any lit aid. The description beside it gives character, colour, period, elevation, range.
	Full description P 16	Fl(3)WRG.15s13m7-5M reads: group-flash 3 · white/red/green sectors · 15-second period · 13 m elevation · 7 to 5 miles range.
	Leading lights P 20	Two lights in transit define the safe track; the firm line is the line to follow.
	Sector light P 40	One light, different colours over different arcs — white keeps you in the fairway, red and green warn you off the sides.

QBuoys & beacons12 symbols

	Port-hand lateral Q 130.1	Red can — leave to port entering with the flood (region A). Light red, any rhythm except Fl(2+1).
	Starboard-hand lateral Q 130.1	Green cone — leave to starboard entering. Light green, any rhythm except Fl(2+1).
	Preferred channel Q 130.1	Banded lateral at a fork: Fl(2+1) light. Main channel lies the OTHER side of the colour it shows.
	North cardinal Q 130.3	Black over yellow, cones both up — pass north. Light: continuous quick or very quick white.
	East cardinal Q 130.3	Black-yellow-black, cones base-to-base — pass east. Q(3)10s or VQ(3)5s.
	South cardinal Q 130.3	Yellow over black, cones both down — pass south. Q(6)+LFl.15s.
	West cardinal Q 130.3	Yellow-black-yellow, cones point-to-point — pass west. Q(9)15s.
	Isolated danger Q 130.4	Black with red band(s), two black spheres — danger beneath, navigable water around. Fl(2) white.
	Safe water Q 130.5	Red and white vertical stripes — safe all round; landfall and mid-channel marks. Iso, Oc, LFl.10s or Mo(A).
	Special mark Q 130.6	Yellow, any shape, X topmark if any — racing marks, outfalls, data buoys. Fl.Y rhythms.
	Perch / withy Q 90	Minor stake marking a drying creek edge — local knowledge in timber form.
	Mooring buoy Q 40	For making fast, not navigation — do not pick one up uninvited.

RFog signals1 symbols

Fog signal

R 1

Arcs at a light or buoy — it sounds in fog; the legend says how (Horn, Bell, Whis, Siren).