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6.2 Azimuths PDF Print E-mail

Azimuth

An azimuth is the direction measured in degrees clockwise from north on an azimuth circle. An azimuth circle consists of 360 degrees. Ninety degrees corresponds to east, 180 degrees is south, 270 degrees is west, and 360 degrees and 0 degrees mark north.

photo of compass rose in desert near NASA DrydenThe word "bearing" is sometimes used interchangeably with azimuth to mean the direction (the degree reading) from one object to another. As shown in Section 6.1, this usage is correct only in the first (NE) quadrant between 0° and 90°.
Example 1 - What is the bearing and azimuth reading of the line?

The azimuth reading is 45° or the bearing is N 45° E.

Notice that in this case the azimuth and bearing are both the same because the direction is in the NE or first quadrant.

Azimuths can also be read from the south. In the previous example, the azimuth reading is 225° from the south. The National Geodetic Survey of the National Oceanic and Atmospheric Administration (NOAA) (formerly the United States Coast and Geodetic Survey) always uses south as the zero direction. In wildland fire service, the azimuth is always read from the north point.

Wind Direction

Azimuth is often used to denote wind direction. Traditionally, wind direction is reported as one of eight compass point (N, NE, E, SE, S, SW, W, NW). However, plots of wind and speed direction often give an azimuth value using 0° and 360° for north, as described above. Winds are named according to the direction from which they are blowing. For instance, a westerly wind blows from the west (or 270°), while a southeasterly wind blows from the southeast (135°).