Cross bearing
A cross bearing ( English cross bearing , in the land surveying Resection ) in the means navigation more precisely when - location - the finding of one's location by determining the directions are where two known locations of the Earth's surface as seen from the location of the navigated from. To do this, the location of these places in the map used must be known beyond any doubt. The directions to be determined are called base lines, their intersection represents the desired location on the map. The slightest error for the location arises if the two base lines are perpendicular to each other and “cross”, which explains the name. The determination of the direction is the actual bearing . If you take a bearing with the eye, the known places must be visible. With radio navigation , only locations marked on the map with appropriate transmitters that can be easily received are suitable.
The method can also be used with more than two known locations, thereby reducing the inaccuracy of the location determination. The desired location is then the centroid suspected the plane defined by the position lines triangle or polygon.
In astronavigation, too, location determination using intersecting stand lines is based on the idea of a cross bearing, although not the targeted objects, but only their pixels are on the surface of the earth.
The cockpit instruments for NDB and VOR show misleading courses . These magnetic courses can be transferred directly to the radio navigation maps, which are also magnetic. However, if you want to transfer the course lines read to an aeronautical chart or nautical chart , you have to convert the magnetic courses into true courses , i.e. H. the respective location dismissal , OM ( variation , VAR) must be taken into account.
In terrestrial navigation , which is mainly used in seafaring , the cross bearing is the classic method of determining position using bearings . You need two prominent points in the terrain of a known position, as well as a (bearing) compass , map, ruler and course triangle . The determined correct courses can be entered directly into the also correct nautical charts ( angle maps, correct alignment of the meridians). The prominent points of known position can also be on the water surface, e.g. B. lightships, drilling platforms, wind turbines, buoys, navigation signs, or on land (church tower, chimney, windmill, mountain peak, cape). What is important is the clear recognizability and the known position of the sounded objects in the nautical chart or according to length and latitude.
literature
- Jeppesen Sanderson: Private pilot FAA practical test study guide: airplane single-engine land. Englewood, Colorado 2000, ISBN 0-88487-265-3 .
- Jeppesen Sanderson: Private Pilot Manual. Englewood, Colorado 2002, ISBN 0-88487-238-6 .
- Jürgen Mies: Funknavigation , Privatpilotenbibliothek series, Volume 3, Motorbuch Verlag, Stuttgart 1995, ISBN 3-613-01648-6 .
- Peter Dogan: The Instrument Flight Training Manual. 1999, ISBN 0-916413-26-8 .
- Walter Air: CVFR textbook. Mariensiel 2001.
- Wolfgang Kühr: The private pilot, flight navigation. Verlag Friedrich Schiffmann, Bergisch Gladbach 1979, ISBN 3-921270-05-7 .
Web links
PDF cross bearing + double bearing, implementation and drawing solution