Usage
If navigating by gyrocompass, the reference direction is true north, in which case the terms true bearing and geodetic bearing are used. In stellar navigation, the reference direction is that of the North Star, Polaris. Generalizing this to two angular dimensions, a bearing is the combination of antenna azimuth and elevation required to point (aim) an antenna in a given direction. The bearing for geostationary satellites is constant. The bearing for polar-orbiting satellites varies continuously.
Moving from A to B along a great circle can be considered as always going in the same direction (the direction of B), but not in the sense of keeping the same bearing, which applies when following a rhumb line. Accordingly, the direction at A of B, expressed as a bearing, is not in general the opposite of the direction at B of A (when traveling on the great circle formed by A and B). For example, assume A and B in the northern hemisphere have the same latitude, and at A the direction to B is eastnortheast. Then going from A to B, one arrives at B with the direction eastsoutheast, and conversely, the direction at B of A is westnorthwest.
Bearings can also be trasmited in to NNE-North North East NNNE-North North North east and ENNE-East North North East.
Read more about this topic: Bearing (navigation), Bearing Measurement
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