What Is a Compass? Definition, Parts, Types and Uses

A compass is an instrument used to find direction. The familiar magnetic compass has a magnetized needle that aligns with Earth’s magnetic field. Once you identify north, you can work out east, south, west and the directions between them.

Here, “compass” means the navigation instrument, not the hinged drawing tool used to make circles.

What does a compass tell you?

A compass gives a reference direction and lets you measure an angle relative to it. That angle is called a bearing.

For example, east is a bearing of 90°, measured clockwise from north. If you point a compass’s travel arrow toward a building and measure 90°, the building lies east of your position using that compass’s north reference.

A compass does not, by itself, tell you:

• Your geographic position or coordinates.
• How far away your destination is.
• Whether the ground between you and the destination is passable.
• Which route is safe or shortest.

Those questions need other information, such as a map, known landmarks and local conditions.

The main parts of a magnetic compass

On a typical baseplate hiking compass, a magnetic needle moves inside a circular housing. A bezel carries the degree scale. The clear baseplate has a straight edge for map work and a direction-of-travel arrow.

Inside the housing, an orienting arrow helps you align the north-seeking needle. A fixed index line marks where to read a bearing.

These parts have different jobs. The needle establishes north; the travel arrow can point at any subject you want to measure. The illustrated guide to reading a compass shows how they work together.

Common types of compass

Type	How it establishes direction	Typical context
Magnetic needle compass	A magnetized needle aligns with the local magnetic field	Hiking, orienteering and basic navigation
Electronic compass	Sensors measure the magnetic field; software calculates heading	Phones and electronic instruments
Gyrocompass	A gyroscopic system uses Earth’s rotation to establish true north	Marine navigation
Solar compass	The Sun’s direction, time and location establish a reference	Surveying and specialized navigation

Not every compass points to magnetic north. A gyrocompass establishes true north by a different principle, while some electronic compasses apply a correction to magnetic measurements.

A basic magnetic needle compass needs no battery. An electronic compass needs power even if it can work without an internet connection.

What is a compass used for?

People use compasses to check which way they are facing, identify a building’s orientation, measure a bearing to a landmark and align a map with the terrain.

In hiking and orienteering, a compass supports navigation alongside a map and route-planning skills. On ships and aircraft, compass instruments are part of a wider navigation system rather than the only source of guidance.

For an everyday direction check, a browser compass can read a compatible phone’s sensors. A computer or phone without suitable sensor access will not supply a live north reference just because it can display a compass dial.

Compass, map and GPS: what is the difference?

A compass tells direction. A map shows the relationship between places. A GPS receiver estimates position using satellite signals.

Phone navigation apps often combine these. Your map can show a location dot from GPS and a pointing direction from the magnetometer. If the pointing arrow is wrong, that does not necessarily mean your GPS position is wrong.

Likewise, knowing that a place is northeast does not identify a route to it. A river, property boundary or steep slope may lie along that line.

What should a beginner learn first?

Start with the four cardinal directions and their degree values. Then learn to distinguish the north-seeking needle from the travel arrow. Practice somewhere familiar before using bearings for route finding.

These guides cover the next steps:

• Compass directions and degrees: the direction chart and bearing tables.
• How does a compass work?: the magnetic principle and phone sensors.
• How to use a compass: practical bearing and map exercises.
• When was the compass invented?: how early magnetic devices developed into navigation instruments.

References

• Britannica: Compass defines compass instruments and their operating principles.
• National Geographic: Compass describes compass types, history and navigation uses.