Taking a bearing refers to measuring the direction from one point to another, either in the field or on a map. A bearing is the measurement of direction between two points and it is typically expressed as an angle, for example 30 degrees. Bearings taken with a compass that has not been adjusted for magnetic declination are called “magnetic bearings.” Whereas bearings taken with a compass that has been adjusted for magnet declination are called “true bearings.” This section focuses on taking a direct and back bearing in the field, but you can learn how to take a bearing on a map here.
Taking a Direct Bearing
A direct bearing is measured from your position towards an object. It tells you the direction from you to the object, destination or landmark. One method for taking a direct bearing is described in the steps below:
- Adjust compass for declination if using the bearing with a map
- Face object and align the direction-of-travel arrow with the object whose bearing you want to measure
- Turn the compass housing until the North end of the magnetic needle is aligned with the orienting arrow
- Read the bearing where the direction of travel arrow or index line meets the dial. This is the direction to the object, expressed as an angle.
Taking a Back Bearing
A back bearing, which is sometimes called backsighting, is the exact opposite of a bearing – it is measured from the object to your position. The back bearing differs by 180° or the opposite direction from the direct bearing.
Two common methods for determining a back bearing include:
- Using a compass – similar process to taking a direct bearing, but instead take a back bearing by aligning the south end of the needle with the orienting arrow.
- Using addition and subtraction.
- If the direct bearing is between zero and 180° add 180° to find the back bearing. For example, if the direct bearing is 60° the back bearing is 240°.
- If the direct bearing is between 180° and 360° subtract 180° to find the back bearing.
Back bearings are important because they can be used to communicate your position to someone else, for example, “I am located 145° from the cell tower.” They are also used when navigating to help ensure you are on course.
**Information adapted from the National Interagency
Incident Management System Basic Land Navigation
Manual, PMS 475 dated June 2007.