| Bearing (navigation) |
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Unless otherwise specified, the reference direction is generally understood to be Magnetic North , in which case the term '' Compass bearing'' is also used. 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 . Generalising this to two angular dimensions, a bearing is the combination of antenna Azimuth and Elevation required to point (aim) an antenna at a spacecraft. The bearing for Geostationary Satellite s 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. For example, A and B on 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. EXTERNAL LINKS |