Indicating Direction Using Azimuth and Bearing

Indicating Direction Using Azimuth and Bearing

A picture of Nicolas MalloyAuthor: Nicolas R. Malloy

As discussed in this chapter, all directional systems measure direction relative to a directional baseline. A directional baseline is a line of reference between a location on the earth and a standard reference point. In most direction systems, the directional baseline refers to true north, which is the northern end of the axis of Earth’s rotation. Azimuth and bearing are examples of directional systems that use true north as a directional baseline. In this activity, you will learn how to indicate direction utilizing both azimuth and bearing and practice how to convert from one directional system to another.

Learning Outcomes

Students who complete this activity should be able to:

  • Explain the difference between azimuth and bearing
  • Indicate a direction using an azimuth
  • Indicate a direction using a bearing
  • Convert directional notation between azimuth and bearing

Azimuth

An azimuth indicates direction by using true north as a directional baseline and measuring clockwise from 0° to 360°. Azimuths are easy to use because one number defines each direction. Treating direction as a single number also makes it simple to use for calculations and in GIS software. Only a single number, written in degrees, indicates an azimuth.

For example, if you were facing true north, and then rotate your body 45 degrees clockwise, your azimuth would be written as “45°.”

An image of an Azimuth of 45 degrees

An azimuth uses a single number, which makes it simple to use for calculations and in GIS software.

When determining a back azimuth, the opposite direction, add 180° if the azimuth is less than 180°. Subtract 180° if the azimuth is greater than 180°. To calculate the back azimuth in this example, add 180 to 45 degrees to get 225°.

An image of a back azimuth of 225 degrees

A back azimuth is sometimes used during a land survey.

On a separate piece of paper, write down the answers to the following questions:

  1. If you were facing true north and turned your body 45 degrees counter-clockwise, what would be your azimuth?
  2. What would be the back azimuth for question 1?
  3. If you were facing south and turned your body 20 degrees clockwise, what would be your azimuth?
  4. What would be the back azimuth for question 3?

Bearing

A bearing indicates direction by using the angular difference away from a north or south baseline, ranging from 0° to 90°. Determining your bearing begins with a north or south baseline, whichever is closer to your direction. You then measure the angle east or west from the baseline. You write the bearing using the following notation: N or S (baseline) degrees° E or W (orientation)

For example, if you were facing true north, and then rotate your body 45 degrees clockwise, your bearing would be written as “N45°E.”

An image of a bearing of N45E

Bearings are not as computer friendly but still used in navigation.

Sometimes you also need to find the opposite direction from which you face. A back bearing is the opposite direction from a bearing and is readily determined by merely changing the letters. The back bearings would be written as “S45°W.”

An image of a back bearing of S45W

A back bearing is used to find the opposite direction you are facing.

On a separate piece of paper, write down the answers to the following questions:

  1. If you were facing true north and turned your body 45 degrees counter-clockwise, what would be your bearing?
  2. What would be the back bearing for question 5?
  3. If you were facing south and turned your body 20 degrees clockwise, what would be your bearing?
  4. What would be the back bearing for question 7?
  5. If you had an azimuth of 175°, how would you write the same direction using a bearing?
  6. If you had a bearing of N25°W, how would you write the same direction using an azimuth?