Compass Guide

Compass Basics

How a Compass Works

A magnetic compass works by aligning a magnetized needle with Earth's magnetic field. The needle's north-seeking end (usually painted red or marked with an arrow) points toward magnetic north. This simple principle has guided explorers for over a thousand years.

Key Compass Components

Cardinal and Intercardinal Directions

The compass dial is divided into 360 degrees, with cardinal directions at key points:

• North (N) - 0° or 360°
• East (E) - 90°
• South (S) - 180°
• West (W) - 270°

Intercardinal directions fall between these: Northeast (45°), Southeast (135°), Southwest (225°), and Northwest (315°).

How to Use a Compass

Taking a Bearing

A bearing is the direction from your current position to a destination, expressed in degrees from north.

1. Hold the compass flat - Keep it level in front of your body, away from metal objects. The needle needs to swing freely.
2. Point the direction-of-travel arrow - Aim the arrow on the baseplate toward your destination (a visible landmark or map point).
3. Rotate the bezel - Turn the compass housing until the orienting arrow aligns with the magnetic needle (red end of needle in the arrow, often called "red in the shed").
4. Read the bearing - The degree marking at the index line (where the direction-of-travel arrow meets the bezel) is your bearing.

Following a Bearing

Once you have a bearing set on your compass, follow it to reach your destination:

1. Set your bearing - Rotate the bezel to your desired heading at the index line.
2. Orient the compass - Hold the compass flat and rotate your body until the magnetic needle aligns with the orienting arrow (red in the shed).
3. Follow the direction-of-travel arrow - Pick a visible landmark in that direction and walk toward it.
4. Repeat - When you reach your landmark, reorient and pick a new landmark. This prevents drifting off course.

Common Mistakes to Avoid

• Metal interference - Keep the compass away from belt buckles, phones, knives, and other metal objects that can deflect the needle.
• Reversed needle - Always ensure you're following the red (north) end of the needle, not the south end, which would send you 180° wrong.
• Tilting the compass - A tilted compass causes the needle to stick or give inaccurate readings. Keep it level.
• Ignoring declination - Magnetic north and true north differ. Failing to account for this causes significant navigation errors over distance.

Map and Compass Navigation

Orienting Your Map

Before using a map, orient it so that the map's north aligns with actual north on the ground:

1. Place your compass on the map with the edge along a north-south grid line (or the map's side edge).
2. Rotate the map and compass together until the needle aligns with the orienting arrow (accounting for declination).
3. The map now shows features in their actual positions relative to you.

Taking a Bearing from a Map

To determine the bearing from your position to a destination shown on the map:

1. Place the compass edge on the map connecting your location and destination.
2. Point the direction-of-travel arrow toward the destination.
3. Rotate the bezel until the orienting lines are parallel to the map's north-south grid lines (orienting arrow pointing to map north).
4. Read the bearing at the index line. Apply declination correction if your compass isn't pre-adjusted.

Triangulation: Finding Your Position

When you can see identifiable landmarks but don't know your exact location:

1. Take a bearing to a visible landmark you can identify on the map.
2. Convert to a map bearing (apply declination) and calculate the back bearing (add or subtract 180°).
3. On the map, draw a line from that landmark at the back bearing angle.
4. Repeat with a second (ideally third) landmark.
5. Your position is where the lines intersect.

For precise triangulation work, a mirror sighting compass like the Silva Expedition 4 provides the accuracy needed for professional navigation.

Aiming Off

When navigating to a feature on a linear landmark (like a trail crossing a river), deliberately aim to one side. That way, when you hit the linear feature, you know which direction to turn. Aiming straight might leave you unsure if your destination is left or right.

Handrails and Catching Features

• Handrails: Linear features (streams, ridges, trails) running roughly parallel to your route. Stay alongside them for easier navigation.
• Catching Features: Prominent features beyond your destination that tell you if you've gone too far. Always identify one before setting off.

Recommended Compasses

After researching and testing numerous compasses, here are our top recommendations for different uses and budgets.

Frequently Asked Questions