In this lesson, I will cover the basics of compass use for navigation. Knowing how to use a compass accurately is crucial for more advanced navigation techniques. It also becomes very important when navigating complex terrain or in poor visibility. Read on for a complete introduction on what is a compass, and how to use it. Followed by an easy step-by-step guide on how to take a bearing. If you have a specific question or aspect of navigating, that you’d like to learn more about, feel free to drop me a message or a comment – and I’d be happy to answer it in a future lesson!
Different Types of Compasses
There are many different types of compasses for different purposes. The types most commonly used for the outdoors include: a basic compass which shows you which way is north but does not have a rotating bezel or any other way to easily align it. A sighting compass is commonly used by the military. They can be very accurate when used by people who know how to use them, but they lack some of the features especially designed for mountain navigation and orienteering. A baseplate, or an orienteering compass, is the most common type for outdoor activities such as hillwalking. It is designed to be used with a map and includes many helpful features, especially for measuring distances from different map scales. It will usually have a rotating bezel, which makes it easy to align it with the map and take accurate bearings.
The Parts of a Compass
- Baseplate – The baseplate houses all of the other parts of the compass, it is clear because it is designed to be placed on top of a map.
- Compass housing – The round compass housing contains the magnetic needle, usually floating in liquid to ensure the needle’s free movement. The housing has the compass points printed on a rotating bezel.
- Compass needle – The red end of the needle points to magnetic north. To ensure it can move freely, it is important to keep your compass flat, both when placing it on the map and when holding it in front of yourself. (Read more about the magnetic north in next week’s lesson).
- Orienting lines – These lines are fixed within the compass housing and are designed to be aligned with the eastings (vertical lines) on the map.
- Orienting arrow – Also fixed within the compass housing, when aligning the orienting lines with the eastings on the map, the orienting arrow needs to point to map north. The orienting arrow also enables conversion between grid and magnetic north when needed.
- Direction of travel arrow – The direction of travel arrow shows the direction that you need to travel along once you have taken a bearing. It is an extension of the index line (number 11).
- Compass scales – These are displayed along the edges of the baseplate for easily measuring distances on the map. The model pictured here has them for both millimeters and inches.
- Romer scales – Allow you to equate measurements on the map to distances on the ground without needing to use conversions. This model has scales for 1:25k, 1:50k and 1:40k maps. Romer scales are also a helpful tool for calculating grid references quickly and accurately.
- Magnifying lens – For easy reading of precise details on the map.
- Magnetic variation – These small numbers inside the compass housing allow adjustment for either magnetic variation or declination.
- Index line – The index line is fixed under the rotating bezel of the compass and it marks the bearing you wish to travel along.
How Does a Compass Work?
A compass works by detecting the Earth’s magnetic fields. All of the above-mentioned compasses are magnetic compasses. They have a free-moving magnetized needle, which points to the Earth’s magnetic north pole. This happens as the delicate needle gets pulled by the magnetic field of the Earth. The needle itself is floating in a liquid and attached to a low friction bearing, which allow it to move freely.
What Are Bearings?
A bearing is the angle between two points. The four cardinal directions (North, East, South and West) are shown on the rotating bezel accompanied by numbers from 0° to 360° between them. The bearing of a direction is the angle between that direction, measured in clockwise direction, and north.
How to Take a Compass Bearing?
The best way to learn how to take a bearing and use it with no mistakes is to create a routine. If you always take the same steps to take a bearing, it will quickly become effortless. In order to take a compass bearing using a map, follow these easy steps:
- Take your map out and hold it flat in front of yourself (in mountain conditions, ideally rest it against a surface, such as your knee, to avoid it blowing away). Find your current location (or last known location) on the map. This is point A.
- Find the location or feature you want to travel to on the map. This is point B.
- Place your compass on the map. Line up the edge of the compass so that it points from point A to point B. Ensure that the direction of travel arrow points towards point B (i.e. direction you want to travel to).
- Turn the rotating bezel until the orienting lines on the base of the housing are parallel with the vertical grid lines on the map (the eastings). Make sure that the orienting arrow is pointing to the top of the map (map north).
- Once you have done this, remove the compass from the map. Be careful to not rotate the bezel again. Ensure that the compass remains flat in your hands in order to not disrupt the needle. (When necessary, adjust for magnetic variation during this step. I will discuss this in more detail in the next lesson).
- Hold the compass in front of your body (chest height is good). Rotate your whole body around until the floating red needle (the north arrow) is inside the orienting arrow. You can think about this as putting the red in the shed.
- The direction of travel arrow now points to where you want to go. Pick something, like a landmark or a feature, in the middle distance directly along that line. Walk to that, check your bearing again, and choose the next feature to walk to. Repeat this until you reach point B.
Well done! You now know how to successfully take a bearing. Once you have reached your intended feature or location, you can either repeat this process to reach the next one along a different bearing or move into using other navigation techniques.
Other in the Compass Corner Series:
This lesson concludes the first part of the Compass Corner navigation series, which has focused on navigation skills for beginners. Next week, tune in for more intermediate navigation skills, starting with a more in-depth looks at bearings, including discussing what is the magnetic variation (and when do we need to care about it) and troubleshooting common mistakes when using bearings.