Imagine this
You are preparing a real trip and use of hand-bearing compass changes the decision. Use this module to explain the cue, the risk, and the next safe action before you move on.
5 lesson sections · 12 quiz questions · 10 flashcards
Day Skipper training module 9 of 17
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Compass
Hand-bearing compass, variation, deviation, and compass conversions.
Use of hand-bearing compassApplication of variation
3 outcomes for this module
- Explain hand-bearing compass, variation, deviation, and compass conversions.
- Apply Use of hand-bearing compass to a realistic onboard situation.
- Recall the core check: true North — geographic north (charts are drawn to true north).
Preview the onboard scenario
You are preparing a real trip and use of hand-bearing compass changes the decision. Use this module to explain the cue, the risk, and the next safe action before you move on.
5 lesson sections · 12 quiz questions · 10 flashcards
Lesson summaries
Use this module hub to choose the right lesson, then open the dedicated lesson page for the complete explanation, worked examples, FAQs, and practice questions.
Three Norths
To understand compass work, you need to know there are three different 'norths'. True North is the geographic North Pole — all charts are aligned to true north. Magnetic North is where a...
- True North — geographic north (charts are drawn to true north)
- Magnetic North — where a compass needle naturally points
Variation
Variation is the angular difference between True North and Magnetic North. It changes slowly over time and varies by location. On a chart, variation is printed on the compass rose — for e...
- Variation = difference between True North and Magnetic North
- Found on the chart compass rose with date and annual change
Deviation
Deviation is the error caused by magnetic influences on YOUR boat — the engine, electronics, metal fittings, and even a mobile phone near the compass can deflect the needle. Unlike variat...
- Deviation = compass error caused by the boat's own magnetic field
- Different on every heading (unlike variation, which is constant for an area)
Converting Between Bearings — CADET and CDMVT
To convert between True, Magnetic, and Compass bearings, you add or subtract Variation and Deviation. The mnemonic CADET tells you whether to add or subtract: Compass + Add + Deviation +...
- CADET: Compass ADd East for True (Compass → True)
- Cadbury (C) Dairy (D) Milk (M) Very (V) Tasty (T)
Using a Hand-Bearing Compass
A hand-bearing compass is a portable compass used to take bearings of objects. Hold it up to your eye, sight on the object through the prism, and read the bearing from the compass card. I...
- Hand-bearing compass gives magnetic bearings when kept clear of local magnetic influences
- Hold away from metal and electronics for accuracy
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