Introduction to Bearings and Basic Terminology

TL;DR

Bearings are directions measured as an angle from North, always in a clockwise direction. There are two main types: compass bearings (like NE) and true bearings (three-digit angles). Understanding these basics helps you describe locations accurately for navigation.

1. The Mental Model

Imagine you're standing still, always facing North. To describe where something else is, you just spin around clockwise until you're looking at it, and the angle you turned is its bearing.

2. The Core Material

When we talk about bearings, we're talking about a way to describe direction using angles. It's super important in navigation, whether you're on a ship, a plane, or just hiking.

The absolute key rules for bearings are:
1. Always start from North: North is your reference point, like 0 degrees on a protractor.
2. Always measure clockwise: You spin to the right from North.
3. Always use three digits for true bearings: Even if it's a small angle, like 5 degrees, you write it as 005°.

Types of Bearings

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There are two main ways to express bearings:

Compass Bearings

These are probably what you're most familiar with. They use the cardinal directions: North (N), East (E), South (S), West (W), and the in-between points like North-East (NE).

• N: North (0° or 360°)
• E: East (90°)
• S: South (180°)
• W: West (270°)
• NE: North-East (45°)
• SE: South-East (135°)
• SW: South-West (225°)
• NW: North-West (315°)

Sometimes you'll see more precise compass bearings, like N30°E, which means 30 degrees from North towards East. Or S60°W, which means 60 degrees from South towards West.

True Bearings

These are more precise and are always expressed as a three-digit number measured clockwise from North. This is the most common type used in professional navigation.

• North is 000° (or 360° if you've gone a full circle).
• East is 090°.
• South is 180°.
• West is 270°.

Let's look at how they relate:

graph TD
    Start["You are here (Origin)"] --> North["Always start from North (000°)"];
    North --> Clockwise["Measure clockwise"];

    subgraph Types of Bearings
        True["True Bearing (e.g., 045°)"] --> ThreeDigits["Always 3 digits"];
        Compass["Compass Bearing (e.g., NE)"] --> CardinalPoints["Uses N, S, E, W"];
    end

    Clockwise --> True;
    Clockwise --> Compass;
    True --> Example1["090° is East"];
    Compass --> Example2["SE is South-East"];

Converting Between Types

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You'll often need to switch between these.

• Compass to True:

  • N45°E is 045°T (True).
  • S30°E means 30° from South towards East. South is 180°, so it's 180° - 30° = 150°T.
  • N60°W means 60° from North towards West. North is 360° (or 0°), so it's 360° - 60° = 300°T.

• True to Compass:

  • 120°T: This is between 90° (E) and 180° (S). It's 180° - 120° = 60° away from South towards East. So, S60°E.
  • 310°T: This is between 270° (W) and 360° (N). It's 360° - 310° = 50° away from North towards West. So, N50°W.

3. Worked Example

Let's say you're at point A and you need to describe the direction to point B.
Imagine North is straight up from point A.
If point B is directly to your East, its true bearing from A would be 090°.
If point B is exactly halfway between North and East, its true bearing would be 045°.
Its compass bearing would be NE.

Now, let's say point B is such that if you draw a line from A to B, and then draw a line directly South from A, the angle between the South line and the A-B line (measured clockwise from South) is 20 degrees.
* First, we know South is 180°.
* Since B is 20° clockwise from South, you add that angle: 180° + 20° = 200°.
* So, the true bearing of B from A is 200°.
* To convert this to a compass bearing: 200° is between South (180°) and West (270°). It's 200° - 180° = 20° away from South towards West. So, the compass bearing is S20°W.

4. Key Takeaways

• Bearings are always measured from North.
• Bearings are always measured in a clockwise direction.
• True bearings use three digits (e.g., 045°, 180°, 275°).
• Compass bearings use cardinal and intercardinal points (N, S, E, W, NE, SE, SW, NW) or specific angles from North/South towards East/West.
• East is 090°, South is 180°, and West is 270° for true bearings.
• Being able to convert between true and compass bearings is a crucial skill.

Common mistakes to avoid:
- Measuring counter-clockwise instead of clockwise.
- Forgetting to use three digits for true bearings (e.g., writing 45° instead of 045°).
- Measuring from East or South instead of always starting from North for true bearings.
- Getting confused when converting from true to compass bearings, especially when crossing the North/South lines.

5. Now Try It

You're at the center of a large field. Your friend is standing at a true bearing of 240° from your position.
1. Draw a simple diagram showing your position, North, and your friend's position.
2. What is the compass bearing to your friend?
3. If your friend walks 50m due East, what would their new true bearing be from your original position? (You don't need a calculator, just state whether it would be greater or less than 240° and why).

Success looks like: You have a clear diagram, you correctly convert 240° to its compass bearing, and you accurately explain the change in the true bearing (and direction) if your friend moves East.