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Bearings can be used to help establish the current position or the correct direction of travel.
They are used in two main ways:
- On a map between two features.
- On the ground between a feature and your current position.

There are specific ways to use bearings to help establish current position (intersection and resection) which are used much less often.

This page covers:
1) What a bearing is
2) How to use a bearing to determine which direction to travel
3) How to use bearings to determine where you are

what are bearings?

Bearings can sometimes seem complicated, and this is more likely if this fundamental question is not understood. A bearing is the angle between one line (either between two locations on a map, or between your position and a feature on the ground) and the line running north. They are counted clockwise, usually in degrees (so a bearing of 360 degrees = a bearing of 0 degrees = north).

For example if a feature is to your west, its bearing from you (you need to specify which feature the bearing is taken from) is 270 degrees.

Military compasses use mils rather than degrees to divide the circle (6400 vs 360). In general this is not that helpful for the recreational user but can be useful to aid range-finding (1mil = 1 m at 1 km). The descriptions below assume that "normal" compasses are being used not lensatic or sighting compasses - these require different techniques.

some good practices:

1) If the bearing is a single or double digit number add zeroes to make it a three digit number when communication - e.g. the bearing of an object east of you would be described as "zero nine zero" degrees rather than "ninety" degrees. This makes communication less error-prone.
2) Always add "magnetic" or "grid" to clarify - this is important whenever the grid magnetic angle is more than a few degrees.

azimuth

The description above is most correctly applied to the term "azimuth"; that term is used relatively little whereas most people will understand what you mean by a bearing of 180 degrees.

using bearings to determine which direction to travel

There are two components of this process (and this assumes you know both where you are and where you want to be - assumptions that are not always true!):
1) Taking a bearing from a map
2) Applying/following that bearing on the ground

taking a bearing from a map

To find the bearing of one location on a map from another use a base plate compass:
Identify both features on the map and be clear which is the "anchor" (often your current location) and which is having the bearing measured from that "anchor"

"Eyeball" which quadrant a bearing will be in - for example if the bearing is between north and east, a value of 225 degrees is clearly wrong.

bearings quadrants.jpg

Lay the compass on the map (make sure the compass is attached to you) so one of the lines on the base plate parallel to the direction of travel arrow passes through both points (exactly). The direction of travel arrow must be pointing towards the point you will be moving towards (or the bearing will be out by 180 degrees). These lines do not get chipped or damaged and will therefore be more accurate than using the long edge of the base plate. A longer base plate makes this easier. Occasionally a straight edge has to be passed between the two points and the compass edge placed against that if the points are too far apart.

Turn the compass housing (without moving the compass out of position - sometimes easier said than done) so the orienting lines in the housing are parallel to the north-south grid lines on the map. You need to view the compass housing from above to do this accurately.

Double check the north end of the orienting lines is pointing north on the map - it is easy to take bearings with an error of 180 degrees.

Read the angle on the compass housing next to the compass direction of travel line: this is the bearing. In effect you are using the compass as a protractor. Do not worry about the "red end" of the floating needle - it does not play a part in this process.

Because the angle (bearing) has been taking relative to the grid lines on the map this is a grid bearing.

Before following the bearing on the ground, adjustment for the grid magnetic angle (the angle between grid north and magnetic north - see here for an explanation of this) will be needed. In the UK at present (2013) magnetic north is usually 0 to 2 degrees west of grid north; add two degrees to the grid bearing to generate the correct magnetic bearing. The magnetic bearing is needed when you will be using a compass to follow a bearing.

videos and links on taking bearings from a map

Video showing the brace position for using a map/compass:


Taking a bearing from a map:


Taking and using bearings:


Taking and using bearings:


The Silva 1-2-3 method


how to take a bearing
finding your way with map and compass (USGS)
Taking and following bearings

following a bearing on the ground

Having obtained a bearing from the map to guide travel, it is important to follow that bearing as accurately as possible.

It can be a matter of life and death to follow bearings very accurately to exit mountain tops safely in poor visibility. The techniques of following a bearing should be practised in good visibility and not used for the first time in darkness or poor weather.

To follow the correct direction of travel:
Double check whether the bearing you have is magnetic or grid. If the latter adjust to generate an accurate magnetic bearing (add 2 in UK).

Rotate the compass housing so the magnetic bearing to follow is next to the direction of travel arrow.

Hold the compass horizontal in front of you with both hands and rotate yourself (NOT the compass housing) until the north end of the needle points to north on the compass housing.

Look up and follow, with your eyes, the direction of travel arrow until a fixed feature on the land is noted. (it sounds obvious but sheep and cattle are no use - they are prone to move!) - this should not be too close otherwise these steps have to be repeated irritatingly often; in poor visibility,though, there may be no alternative.

Double check that feature is in the correct direction.

Walk towards that feature - there is no need to look at your compass while you are doing this (doing so may led to errors of lateral drift).

When you reach the feature, assuming the bearing on which you wish to travel is unchanged, repeat the process. If you will be following the same bearing do not rotate the compass housing while walking.

walking on a bearing:


If you are lucky you may find there are two features that both lie on the desired bearing - when you move keep these lined up and you will be able to follow the bearing accurately.

Beware of the tendency to drift downhill or downwind when following a bearing

using a back bearing to increase accuracy

If the point from which you departed is visible you can check your accuracy by taking a back bearing. To do this point the direction of travel arrow at the feature you left without rotating the compass housing. If you have followed the bearing accurately the south end of the compass needle will be pointing to north on the compass housing (this is because the back bearing will be directly - 180 degrees - opposite the bearing).

see this page for following a bearing in poor visibility

following bearings going round an obstacle

There is a technique to navigate round an obstacle (e.g. a pond or a sink hole) while following a bearing and, often, measuring distance (counting paces)
The key is to make the turns exactly 90 degrees

box_bearing.jpg
box_bearing.jpg


using bearings to determine where you are

There are two components: taking a bearing "on the ground" (i.e. with "real " features), then applying that information to the map.
To do this there needs to be at least one feature you can see on the ground and which is also on the map - and you must be confident you have the correct feature.

taking a bearing on the ground

Stand facing the feature with the compass horizontal in front of you, or adopt the brace position, with the direction of travel arrow pointing to the feature. This needs to be accurate. Do not rush this stage.

Rotate the compass housing (but NOT the base plate) until the north end of the needle points to north on the housing. Check that the direction of travel arrow is still pointing at the "target".

Read off the bearing at the direction of travel arrow: this is the magnetic bearing from your position to the feature (i.e. the bearing of the feature from your position).

video showing how to use the brace position when taking a bearing from a feature on the ground:


video showing how to use the "centre hold" technique (my personal preference, though I would suggest whenever possible using both hands to hold the compass and holding both forearms tight against the abdomen)

applying that to the map

Adjust for grid magnetic angle (ie rotate the compass housing) - in the UK take 2 degrees from the bearing to create the grid bearing and set that on the compass by rotating the compass housing so the grid bearing lies at the direction of travel arrow. Do not rotate the compass housing again during this process.

Place a line in the base plate (or the edge of the compass) so that it passes through the feature that has been identified on the ground and the map.

Keeping the line or edge passing through your position rotate the whole compass (NOT the compass housing) until
1) the north south orienting lines in the compass housing are parallel to the north south grid lines on the map AND
2) with north end of the orienting lines point to the north edge of the map.

The compass line/edge will now pass through/point towards your position in the opposite direction to the direction of travel arrow.


A similar process can be used to identify a feature that can be seen on the ground but you're not sure what is in when just using the map set (this assumes you know your current location). The difference here is the direction of travel arrow will point from your location to the feature.

For example:
You are at the trig point on Cross Fell in good visibility (does not happen often!) and can see a strange dome.
You take the bearing of the dome from the trig point: it is 134 degrees (this is a magnetic bearing)
The grid bearing is therefore 132 degrees (assume GMA is 2 degrees)
When you apply this to the map you find it passes through the radar station on the summit of Great Dunn Fell - this is the dome.

cross_fell.JPG
cross_fell.JPG



see the page on relocation for information on intersection and resection