Nautical Terms and Charts Flashcards
The direction towards the wind
Windward
The direction away from the wind
Leeward (“Loo-erd”)
Drift due to the wind
Leeway (“Loo-way”)
The widest part of the boat
Beam
90 degrees to the right
Starboard beam
90 degrees to the left
Port beam
Left
Port
Right
Starboard
Port
Left
Starboard
Right
What colour is the port navigation light?
Red
Aft
Towards the stern
Points of Sail:
What is “Close Hauled”
On the border of the “No sail zone” - 45 degrees from “head to wind”.
Physics:
- High wind fraction hitting the hull
- Fair wind hitting sail (narrow)
- Small angle of wind ΔV
- Fair force from wind on sails
- Force on sails is slightly forward
- Boat “generates its own wind”
Points of Sail:
What is “Head to Wind”
When the boat is heading towards the wind - Ideal for stopping the boat.
Physics:
- All wind hitting hull
- No wind hitting sail
- No wind ΔV
- No angle of wind ΔV
- No force from wind on sails
- Force on sails is over 90 degrees to boat direction.
Points of Sail:
What is the “No Sail Zone”?
A zone 45 degrees either side of the “Head to Wind”.
Physics:
- High wind fraction hitting hull
- Little wind hitting sail (narrow)
- Tiny angle of wind ΔV
- Little force from wind on sails
- Any force on sail is mostly perpendicular
Points of Sail:
What is “Close Reach”?
Partially into the wind, between “Beam Reach” and “Close Hauled”.
Physics:
- Less wind fraction hitting hull
- Fair wind hitting sail
- Larger angle of wind ΔV
- Less force from wind on sails
- Force on sails is slightly forward
- Boat “generates its own wind” and can go faster.
Points of Sail:
What is “Beam Reach”?
Beam points into wind- bow points 90 degrees to wind.
Physics:
- Smaller wind fraction hitting hull.
- Good wind hitting sail
- Large angle of wind ΔV
- Good force from wind on sails
- Force on sails is slightly forward
- Cannot go faster than wind.
Points of Sail:
What is “Broad Reach”?
Between “Beam Reach” and “Running” - ~95-175 degrees from the wind.
Physics:
- Small wind fraction hitting hull.
- Lots of wind hitting sail
- Very large angle of wind ΔV
- Large change in wind ΔV
- Good force from wind on sails
- Force on sails can be entirely forward.
- Cannot go faster than wind
Points of Sail:
What is “Running”?
180 degrees from the wind.
Physics:
- Tiny wind fraction hitting hull.
- Most of the wind hitting sail.
- Wind is “stopped”.
- Good force from wind on sails
- Force on sails can entirely forward.
- Cannot go faster than wind.
If a sail is “backed”, where is the leech facing?
In a windward direction
- Foresail is backed when heaving to.
- Useful in MOB manoeuvres.
abeam
-Roughly 90 degrees to the boat
Nautical Miles : Degrees [Give Ratio]
60 : 1
Degrees : Earth Circumferences [Give Ratio]
360 : 1
What is the Earth’s circumference [Nautical miles]?
21600 Nautical Miles
Cables : Nautical Miles
10 : 1
How long is a cable?
185m
Given a cable is 185m, how long is the Earth’s circumference [in m]?
39,960,000m
185m x 10 x 60 x 360
Nautical Miles : Minutes of latitude?
1 : 1
What happens to the size of a minute of longitude as you go North?
A minute of longitude gets shorter the further North you go. At the poles, minutes of longitude are 0m in length.
What is “Chart datum”?
The lowest the tide of a chart should conceivably go.
-Depths are measured from this.
What are bridge/cable clearance heights measured from?
HAT
-Highest Astronomical Tide
What are lighthouse/buildings heights measured from?
MHWS
-Mean High-Water Springs
What are chart heights and depths measured in?
Meters.
Admiralty charts: What do the following shadings mean? -White -Blue -Green -Yellow
- White = >10m Depth
- Blue = <10m Depth
- Green = Uncovered at chart datum
- Yellow = Land
What must be done to the magnetic North Pole when charting?
It must be corrected to find the true North Pole
-Called “Variation”
If the magnetic pole is “left” of the true pole, from where the vessel is, what is this called?
West variation
If the magnetic pole is “right” of the true pole, from where the vessel is, what is this called?
East variation
When given one of a chart’s compass roses, the arrow pointing to Magnetic North has this written on it:
“3°40’W 2021 (8’E)”
What does this mean?
Magnetic North is 3 degrees, 40 minutes west of True North in 2021. Every year Magnetic North is moving 8 minutes East.
This is also a West variation.
When given one of a chart’s compass roses, the arrow pointing to Magnetic North has this written on it:
“3°40’W 2021 (8’E)”
What should an updated compass rose say in 2022?
3°32’W 2022 (8’E)
Say and explain the pneumonic for westerly variation.
“MAG TO GRID = GET RID
GRID TO MAG = ADD”
- Magnetic to grid (chart) = get rid (subtract) variation
- Grid (chart) to magnetic = Add variation
Say and explain the pneumonic for easterly or westerly variation
“If the error is WEST, then magnetic will be BEST
If the error is EAST, then magnetic will be LEAST”
- Magnetic bearing with Westerly variation will be best (Greater) than the true bearing.
- Magnetic bearing with Easterly variation will be least (Lesser) than the true bearing.
-This, for me at least. is quite hard to get your head around. I recommend drawing it out on paper.
When using a compass, what must you be wary of leaving/holding near them?
Electromagnetic or ferrous materials like phones etc.
-Can interfere with where “Magnetic north” is
When you get a compass swung (Akin to a repair), what do you receive with it?
A deviation card.
- This card tells you the error in magnetic North that this particular compass + vessel has.
- 2D grid: Bearing (y axis) vs Deviation (x axis)
What does °C mean?
“Compas Bearing”
- This is either fully adjusted from the chart or
- Needs to be adjusted if using it for the chart.
What is the Equation for °C?
°C = Compass Deviation + Magnetic Variation + °T
e. g.
- Chart says heading is 245°T
- Variation on compass rose is +4°W
- Deviation card for 245 degrees is +1°W
- °C = 1 + 4 + 245 = 250°
What does °T mean?
“True bearing”
- This is the bearing shown on the chart
- Needs to be adjusted to get a compass bearing
Convert this true bearing to magnetic:
126°T Variation 4°W
130°C
WEST = Magnetic is BEST
Convert this true bearing to magnetic:
358°T Variation 6°W
004°C
WEST = Magnetic is BEST: 364° = 004°
Convert this true bearing to magnetic:
180°T Variation 10°E
170°C
EAST = Magnetic is LEAST
Convert this magnetic bearing to true:
324°M Variation 3°W
321°T
WEST = Magnetic is BEST
Convert this magnetic bearing to true:
002°M Variation 10°W
352°T
WEST = Magnetic is BEST
Convert this magnetic bearing to true:
270°M Variation 5°E
275°T
EAST = Magnetic is LEAST
Variation is 5°W. No Deviation card. The heading should be 045°T, but your compass is reading 055°C. What is the deviation?
5°W
- Variation is west (WEST = magnetic is best)
- 045°T + 5° = 050°M
- 050°M + D°W = 055°C
- D°W = 055°C - 050°M
Chart Symbols (With lack of image) What does this mean? -------------|-- 1600
Dead reckoning (DR).
Chart Symbols (With lack of image) What does this mean? -------------Δ 0800
Estimated Position (EP).
Chart Symbols (With lack of image) What does this mean? [Circle with dot in it] 1600 or [circle with 3 arrows pointing out] 0745
Fix (Observed position).
Chart Symbols (With lack of image) What does this mean? [Square with central cross going over square's borders] 1300
Waypoint.
Chart Symbols (With lack of image) What does this mean? -------------->
Line of position.
Chart Symbols (With lack of image) What does this mean? [Bendy double-ended arrow]
Range.
Chart Symbols (With lack of image) What does this mean? [Double ended arrow on contour line]
Depth contour line.
Chart Symbols (With lack of image) What does this mean? --------->--------
Course through the water.
-Course taken off the distance travelled (on log) and bearing the boat was facing + leeway adjustment.
Chart Symbols (With lack of image) What does this mean? --------->>---------
Course over ground.
- Course through water + adjustments for wind and tide.
- “Course over the ground I.E. Seabed”.
Chart Symbols (With lack of image) What does this mean? --------->>>---------
Tidal stream.
-Adjustment bearing used to work out “course over ground”.
How often to neap and spring tides occur?
Fortnightly.
When do spring tides occur?
When there is a full moon or a new moon.
- Moon is “working with” the sun to produce the high tide.
- Seeing as the moon cycle is a month-long, these occur fortnightly
When do neap tides occur?
When there is a half-moon.
- Moon is “working against” the sun to produce high tides.
- Seeing as there are half-moons twice in a moon cycle, these happen fortnightly.
What are the six defined tide levels?
- HAT - Highest Astronomical Tide
- MHWS - Mean High Water Spring
- MHWN - Mean High Water Neap
- MLWN - Mean Low Water Neap
- MLWS - Mean Low Water Spring
- Chart Datum / LAT - Lowest Astronomical Tide.
Where is “charted depth” measured from?
The chart datum.
At what level would a charted “green” area definitely be completely covered by water
MHWS - Mean High Water Spring
-More specifically you can see how far above chart datum it would be covered.
On a tide table, what must be done for times on an un-shaded day?
An hour must be added to the times, as these are set to summer time.
On a tide table, how can you distinguish a neap, a spring, and any other day?
- Springs’ dates are coloured red.
- Neaps’ dates are coloured blue.
- Other dates are black.
What kind of tide has a greater range? Spring or neap?
Spring tides have a greater range.
Talk through the steps of checking what time the tide will be at a certain level.
- 1: Get a tide curve and a tide table for the area.
- 2: Look at the day you want on the tide chart, and transfer the time of high OR low water to the tide curve.
- 3: On the bottom scale, plot where low water is from the tide table, do the same at the top scale for high water.
- 4: Draw a line between the two points.
- 5: Pick the height you’re interested in, and draw 3 lines, consecutively perpendicular, from the scale to the drawn line to the appropriate curve (dependent on whether it is rising, falling, spring, or neap), then to the time.
How much clearance under your keel do you generally need to have at any time?
At least 1m
If you have a draught of 3.2m, and chart datum is 3m, what is the minimum height low tide can be if you want to anchor?
Low tide = 1.2m
- Take draught + 1m clearance = 4.2m
- CD = 3m
- 4.2 - 3 = 1.2m
Nwelyn high water is -0040h and -0110h compared to Plymouth at 0000h/1200h and 0600/1800h respectively.
If high water in Plymouth on the 16th of October is at 0801h and 2014h, what times is highwater in Nwelyn?
0701h and 1914h
- 0801 is between 0600 (-0110h = -70min) and 1200 (-40min).
- 70 - 40 = 30min
- 0801h is 1/3 between 0600h and 1200h
- 30min x 1/3 = 10
- 70min - 10min = 60mins
- 0801 - 60mins = 0701.
On a tidal diamond table, there are 4 numbers in each row:
-4 - 034 - 0.9 - 0.5
What do they each mean?
- -4 Hours from high tide.
- 034°T direction of tide flow.
- 0.9 knots at spring tide.
- 0.5 knots at neap tide.
GPS, what is:
COG
SOG
ETA
- Course Over Ground
- Speed Over Ground
- Estimated Time of Arrival
Fixing:
What is a “transit”?
When two or more objects are aligned, giving an instant indication that you are on the transit line.
Fixing:
In a 3 point fix, which bearing should you take last?
The bearing closest to the direction of the beam.
-The angle of this bearing will change the fastest, as your vessel moves past it.
Fixing:
What is a “cocked hat”?
A triangle produced from the inaccurate taking of a 3 point fix. Leads to an area of uncertainty.
-At least one of them should be retaken to confirm the position.
“Course to steer” plotting:
When marking points, what do points A, B, C, and D represent?
A- Current position
B- Desired destination
C- Position tide will take the vessel after the time we predict it will take to get to B.
D- Position the vessel will end at, if we adjust the course to steer, accounting for the tidal stream.
“Course to steer” plotting:
What points do you measure between to find the speed over the ground?
A and D
- A = Initial Position
- D = Final position (e.g, after an hour), adjusted for tidal flow.
“Course to steer” plotting:
For winds above 7 knots, what system works well for adjusting course?
Assume you’ll be blown 2° off course for every increase in “Beaufort Wind Force”.
- E.g., Force 3 gives 6° of leeway, force 5 gives 10° of leeway.
- It is a rough system and will leave you, if anything, upwind of your destination.
Buoys/Beacons:
How can you remember the colour scheme of all 4 cardinal buoys?
The arrows point to where the black colour is.
E.g., Two downwards arrows = South (rotated 90 degrees clockwise). Colour: yellow=top and black=bottom.
Buoys/Beacons:
What is the colour and symbol for a North cardinal buoy?
Two arrows pointing upwards. Colour = Black top, yellow bottom.
Buoys/Beacons:
What is the colour and symbol for an East cardinal buoy?
Two arrows pointing outwards. Colour = Black top, yellow middle, black bottom.
Buoys/Beacons:
What is the colour and symbol for a South cardinal buoy?
Two arrows pointing downwards. Colour = Yellow top, black bottom.
Buoys/Beacons:
What is the colour and symbol for a West cardinal buoy?
Two arrows pointing inwards. Colour = Yellow top, black middle, yellow bottom.
Buoys/Beacons:
How do Cardinal buoys flash?
Think CLOCK
- North: Flashes continuously (12)
- East: Flashes 3 times
- South: Flashes 6 times + 1 long flash
- West: Flashes 9 times.
Buoys/Beacons:
Describe the “Isolated Danger Mark”.
- Sits on top of the danger, but clear water around.
- Black, Red, Black.
- Two black balls on top.
- Light: White, flashing in 2s.
Buoys/Beacons:
Describe the “Safe Water Mark”.
- Marks the start of a safe buoy channel.
- Red, White.
- Light: White, isophase or occulting.
Buoys/Beacons:
Describe the “Temporary Wreck Mark”.
- Marks recent wrecks in shipping lanes
- Yellow, blue.
- Light: Alternating blue and yellow.
Buoys/Beacons:
Describe the IALA A “Lateral Marks”.
- Port and starboard-hand posts for coming upstream.
- Port: Red. Starboard: Green.
- Port: Can-shaped. Starboard: Conical-shaped.
Buoys/Beacons:
Describe the IALA A “Preferred channel” mark.
At the start of two split channels.
-If buoy should be on your port side for “preferred channel”, Colour = Red, Green, Red. +Can-shaped + “2+1” red light pattern.
-If buoy should be on your starboard side for “preferred channel”, Colour = Green, Red, Green. +Cone-shaped + “2+1” green light pattern.
Buoys/Beacons:
What is the difference between “occult”, “flashing”, and “isoform” lights?
- Occult: Period of light is longer than the period of dark.
- Flashing: Period of dark longer than the period of light.
- Isoform: Period of dark and light are equal.
Buoys/Beacons:
What is the major difference in IALA B areas compared to A?
- Port and starboard shapes are the same when entering a channel.
- Port and starboard colours are swapped.
Buoys/Beacons:
What are fixed lights?
Lights that show the extremities of a land-feature
-2FR (vert) and 2FG (vert) (Port and Starboard).
Buoys/Beacons:
Lighthouses: What would this signify:
Fl(3)WR.20s 14/12M
- Flashing 3 Times
- White sector
- Red sector (rocky areas, normally)
- Flashes 3 times every 20 seconds
- Nominal range (white) is 14 miles
- Nominal range (red) = 12 miles.
Buoys/Beacons:
-What colour are special marks and what do they signify?
- Yellow
- They signify a multitude of things, including a racing zone, skiing areas, shooting range borders, etc.
International Port Entry Signals:
What do 3x red lights generally mean?
Do not proceed.
- FLASHING = Serious emergency- All vessels must stop.
- +1x yellow = Can proceed outside the main channel.
International Port Entry Signals:
What do green lights generally mean?
Proceed.
- 3x Green = 1-way.
- 2x Green +Central white = only when instructed.
- 2x Green +Central white +Yellow = only when instructed except outside main channel,
- 2x Green +Lower white = Two-way traffic.
Wind:
In the Northern Hemisphere, how does the wind move around zones of high and low pressure?
- High-Pressure: Wind moves clockwise.
- Low-Pressure Wind moves anticlockwise.
Wind:
Why can there sometimes be a “sea breeze” and “land breeze”.
In the morning, the land heats up faster than the sea, causing a convection current to pull cold air in.
At night, the land loses heat faster than the sea, causing a convection current to push cold air out.
-Can be severe if there is a mountain range.
Wind:
Who broadcasts maritime safety information in the UK?
HM Coastguard.
Wind:
What does an “imminent”, “Soon”, and “later” warning mean when referring to weather?
- Imminent = within 6 hours of warning
- Soon = within 6-12 hours of warning.
- Later = more than 12 hours after warning.
Wind:
When is a strong wind warning issued?
When the wind is expected to reach force 6.
What is a “backing” and “veering” wind?
Backing: When the wind changes in an anticlockwise direction
Veering: When the wind changes in a clockwise direction.
