Azimuth refers to an angular measure of direction. It is measured in one of two ways: degrees clockwise from north, or degrees clockwise from south. When measured from north, 0° = north, 90° = east, 180° = south, and 270° or -90° = west. If measured from south, 0° = south, 90° = west, 180° = north, and 270° or -90° = east.

Historically, astronomers and geodesists have measured azimuth from the south, and plane surveyors have measured from north. To add to the confusion, navigators historically measured from the north if they were in the northern hemisphere, and from the south if they were in the southern hemisphere.

The historical difference between geodetic surveying and plane surveying can lead to confusion in datasheet descriptions, especially if the description is from an old report. The azimuths in the box score are now consistently measured from the north. However, if the text of a recovery report mentions an azimuth, it may have been measured either from the north or south. If the report is old, it is more likely to have been measured from the south. A recent report is more likely to have been measured from the north.

An azimuth may be measured from true north or from magnetic north. It is important to know which was used, since the magnetic declination can be significant. In the United States, interpreting the azimuth incorrectly could lead to an error of as much as 25 degrees.


azimuth (last edited 2009-03-21 22:54:02 by JimIrwin)