Skip to content
Practical Skills

How a Compass Works and Why It Matters

Ages 10–14 25 min read Intermediate

A compass is one of the simplest, most reliable navigation tools ever invented. It has no batteries, needs no signal, and works everywhere on Earth. It does one thing: points north. But that one thing, combined with a map, is enough to navigate anywhere.

How It Works

Earth has a magnetic field generated by its molten iron core. A compass needle is a small magnet that aligns with this field, pointing toward magnetic north — which is close to (but not exactly at) true north (the geographic North Pole).

The difference between magnetic north and true north is called magnetic declination. In eastern Australia, this is approximately 10-12° east. For basic navigation, this small difference often doesn't matter, but for precise navigation over long distances, it must be accounted for.

Parts of a Compass

  • Magnetic needle: Red end points north
  • Compass housing (bezel): Rotating ring with degree markings (0-360°)
  • Baseplate: Transparent plate with ruler markings and direction-of-travel arrow
  • Orienting arrow: Fixed arrow inside the housing — you align the needle with this
  • Orienting lines: Parallel lines in the housing — align with grid lines on the map

Basic Compass Use

Finding North

Hold the compass flat. Let the needle settle. The red end points north. Rotate yourself until the red needle sits inside the orienting arrow ("red in the shed"). You're now facing north.

Orienting the Map

Place the compass on the map with the orienting lines aligned with the map's grid lines. Rotate the map and compass together until the red needle sits in the orienting arrow. The map now matches the real landscape around you.

Walking on a Bearing

  1. On the map, place the compass edge along your intended line of travel.
  2. Rotate the bezel until the orienting lines align with the map's north-south grid lines.
  3. Read the bearing number at the direction-of-travel arrow.
  4. Hold the compass in front of you. Turn your body until red is in the shed.
  5. Walk in the direction the travel arrow points.

Tonight's Question

"Which direction does our house face? Without looking at a phone, can anyone point north right now?"

Check with a compass or phone compass afterwards!

Compass Treasure Hunt

  1. Buy or borrow a compass (basic compasses cost $10-20).
  2. In a park or garden, set up a treasure hunt using compass bearings.
  3. "Walk 50 paces on bearing 045°. Then 30 paces on bearing 180°. Treasure is here."
  4. Take turns creating and following compass courses.
  5. Start simple. Add complexity as confidence grows.

Go Further

  • Research: How was the compass invented? (Hint: Chinese navigators, around 200 BCE.)
  • Skill: Learn to find south using an analogue watch (point the 12 at the sun; halfway between 12 and the hour hand is north in the Southern Hemisphere).
  • Book: Be Expert with Map and Compass by Björn Kjellström (2010).
  • Question: What happens to compasses near the magnetic poles? (They become unreliable as the magnetic field becomes vertical.)

What We Simplified

  • Magnetic declination changes over time. Earth's magnetic field shifts slowly. Declination values on old maps may be outdated.
  • Compasses can be affected by metal and electronics. Holding a compass near a car, phone, or metal fence gives false readings.
  • Southern Hemisphere compasses are different. The needle is balanced differently to account for the magnetic field angle. A Northern Hemisphere compass may not work well in Australia.

Sources

  • Kjellström, B. (2010). Be Expert with Map and Compass. Wiley.
  • Geoscience Australia. "Magnetic Declination." ga.gov.au
  • Bushwalking NSW. "Navigation Skills." Bushwalking NSW

Want to track progress and save lessons?

Create a free family account. No credit card, no catch — just a place to keep track of what your family is learning.

Create Free Account