What Is a Compass?
A compass is a navigation instrument that uses Earth's magnetic field to indicate the direction of magnetic north. A magnetised needle inside the compass always points toward the magnetic north pole, allowing you to determine your direction and navigate.
The fundamental directions measured by a compass are called the cardinal points:
- North (N)
- South (S)
- East (E)
- West (W)
Cardinal and Intercardinal Directions
Beyond the four cardinal points, the compass is further divided:
Intercardinal (ordinal) points — 45° between cardinal directions:
- Northeast (NE), Northwest (NW), Southeast (SE), Southwest (SW)
Secondary intercardinal points — 22.5° between each intercardinal and cardinal:
- NNE, ENE, ESE, SSE, SSW, WSW, WNW, NNW
A compass can be divided into 360 degrees starting from North (0°/360°), moving clockwise through East (90°), South (180°), West (270°), and back to North (360°).
The Chinese are credited with inventing the magnetic compass in the 11th century (Song Dynasty). It was used for navigation in Europe from the 12th century onward. Before the compass, sailors relied on stars (especially the North Star, Polaris) to determine direction at night — but this was impossible on cloudy days or in storms.
Compass Bearings
A bearing is a three-digit number (from 000° to 360°) that gives a precise direction:
- North = 000° (or 360°)
- East = 090°
- South = 180°
- West = 270°
- Northeast = 045°
Using bearings
You are at a campsite and need to walk to a shelter. The shelter is in the direction of 135° from the campsite.
135° is between East (090°) and South (180°) — this is the Southeast direction. Walk southeast.
True North vs Magnetic North
True north is the direction of the geographic North Pole (Earth's axis of rotation). Magnetic north is the direction a compass needle points — toward the magnetic north pole, which is not exactly the same as true north. The angle between them at any location is called the magnetic declination (or variation).
Maps usually show the difference between magnetic and grid north, which must be accounted for in precise navigation.
A simple memory aid for the order of compass points: Never Eat Shredded Wheat (NESW — going clockwise starting from North). For 8 points: Naughty Elephants Squirt Water — North East, South West (going NE, SE, SW, NW to return full circle).
Using a Compass with a Map
To navigate with a map and compass:
- Place the compass on the map so the direction of travel arrow points the way you want to go.
- Rotate the compass housing until the compass lines align with the map's north lines.
- Hold the compass level so the needle can swing freely.
- Rotate your whole body until the red end of the needle points to the north mark.
- The direction of travel arrow now points the way to go.
Real world: Columbus and compass navigation across the Atlantic
Christopher Columbus's 1492 voyage used a magnetic compass to navigate the Atlantic — but he faced a problem: magnetic north and true north differ. As he sailed westward, his compass drifted noticeably. His crew grew alarmed, fearing the compass was broken. Columbus understood magnetic declination and secretly corrected his compass readings to avoid panic. He kept two logs — one accurate (private) and one slightly falsified (shown to the crew) to prevent mutiny about distance travelled. This shows how crucial accurate compass knowledge was even 500 years ago.
Real world: Military bearings and the D-Day landings
The Allied D-Day landings (June 6, 1944) required coordinated navigation by thousands of ships, planes, and soldiers. Military commanders used compass bearings to assign each unit to attack specific beaches (Utah, Omaha, Gold, Juno, Sword) at exact angles to avoid friendly fire. Paratroopers dropped at night used compass bearings to navigate to their objectives in the dark. Errors in bearing caused some paratroopers to land miles off course, showing how a small degree error in compass navigation compounds over distance.
Real world: Orienteering — using compass and map together
Orienteering is a competitive sport where participants use a detailed topographic map and compass to navigate between checkpoints in the shortest time. World championships attract athletes from 70+ countries. Competitors must take precise compass bearings, count their paces to measure distances, and read contour lines to understand terrain — all at running pace. Finland and Sweden dominate world orienteering due to their long tradition of outdoor navigation skills in forested terrain, where GPS often fails or is not permitted in competition.
Where do you see this in real life? Next time you use Google Maps or Apple Maps, notice that the compass rose or north arrow is always present. If you rotate your phone, the map rotates but the north indicator stays consistent. Try finding your school on Google Maps and checking which direction is north — then step outside and use the phone compass to verify. Does your building face north, south, east, or west?
Practice Problems
A hiker walks on a bearing of 270°. In which compass direction are they heading?
Show answer
What is the difference between a cardinal direction and a bearing?