Taking Bearings (Direct and Back) (Lat/Lon)

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:

  1. Adjust compass for declination if using the bearing with a map
  2. Face object and align the direction-of-travel arrow with the object whose bearing you want to measure
  3. Turn the compass housing until the North end of the magnetic needle is aligned with the orienting arrow
  4. 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.

navigation_pms4-5

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.

navigation_pms4-6

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.

 

[Continue to Following Bearings]

**Information adapted from the National Interagency
Incident Management System Basic Land Navigation
Manual, PMS 475 dated June 2007.