With the basics perfected close to home, it’s time to move further afield as Lyle Brotherton shares more key skills in Part 4 of our series...
"In this part we are working with bearings, the backbone of all navigation. Even for experienced navigators it’s good to refresh your knowledge and test exactly how accurate you are. An error of just 5° over one kilometre will result in you missing your target by more than 87m; and in poor visibility or at night, this is a real game-changer!"
Taking a bearing
There are two ways of taking a bearing: one is by looking directly at the object and using a compass to walk to it; the other is by using a map. Buy an OS 1:25,000 (Explorer) map of your local area and take this with your compass to your local park, where you can perfect both methods.
Estimate what you think the bearing is going to be, for either method, before you measure it – and if the bearing you then measure differs significantly from your estimation, question why this is before committing yourself to it.
To minimise error, make sure that you are always workingon as stable and level a surface as possible, ideally adopting the ‘brace’ position (below) – and try to make this standard practice.
Taking a bearing to a visible object using your compass
- Facing the identifiable feature to which you wish to take a bearing, assume the brace position to create a solid and stable platform (see above). Place the compass on your knee and point the direction-of-travel arrow on the compass baseplate towards your identifiable feature. Let the compass needle float freely, and it will point to magnetic north.
- Move your head directly over the compass housing to avoid creating parallax – an error whereby your line of sight and the compass needle are not aligned.
- With one hand, hold the compass still on your knee and rotate the bezel until the red orientating arrow is exactly underneath the red north of your needle. The north on your bezel will match the north of your needle.
- Check again that the compass baseplate arrow is pointing exactly towards your identifiable feature, and that the housing arrow and needle are in perfect alignment.
- The reading at the compass index is your magnetic bearing to this target. Do not move the bezel again.
Taking a bearing using your map
- Assume the brace position and place the map on your thigh. Identify where you are on the map (Point A) and the feature you wish to take a bearing to (Point B).
- Use the ruler line on the compass to join Point A to Point B, making sure that the arrow on the compass points in the direction you wish to go. Note: you can ignore the compass needle as it is not required for this technique.
- Rotate the compass bezel until the N on the bezel points north on the map (always the top of the map). Align the compass dial orientating lines so they are parallel with the map’s vertical blue grid lines. The bearing to this object is indicated at the index (line or arrow at the 'top' of the dial). It's worth trying to remember this number. To maximise accuracy when following this bearing, you would need to adjust for magnetic declination, which we will cover in a later issue.
Walking on a compass bearing
With the bearing set, hold the compass squarely out in front of you at about waist height and lean slightly over to look down on it. Let the needle float freely and it will point to magnetic north.
Rotate your body, not the compass, until the red end of the compass needle (north) is exactly over and aligned with the red arrow in the bottom of the compass housing. The front of the compass with the direction-oftravel arrow is now pointing towards your destination. Look directly in this direction and line up a distant landmark.
Testing your proficiency
Here’s the smart part! You can easily test how accurately you have measured your bearings for both methods, and if you make it common practice you will continue to improve your skill level.
When using your compass to take a bearing to a visible object, travel to this object and now take a bearing, using your compass, from where you started. It should be exactly 180° different. A quick test is to glance and see if the white end of your compass needle is pointing to your original bearing when you are taking this bearing back to it.
To test your map bearing skills, take the bearing from Point B to Point A; this should be exactly 180° different. These are called ‘back bearings’ and they will be useful when you learn to locate your position, which we will cover in a later issue along with magnetic declination.