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A bearing compass, is a nautical instrument used to determine the bearing of observed objects. (Bearing: angle formed by the north and the visual to a certain object in the sea or ashore). (Bearing: angle formed by the north and the visual to a certain object in the sea or ashore).
A compass rose, showing absolute bearings in degrees. In nautical navigation the absolute bearing is the clockwise angle between north and an object observed from the vessel. If the north used as reference is the true geographical north then the bearing is a true bearing whereas if the reference used is magnetic north then the bearing is a ...
Compass surveying is a type of surveying in which the directions of surveying lines are determined with a magnetic compass, and the length of the surveying lines are measured with a tape or chain or laser range finder. [2] The compass is generally used to run a traverse line. The compass calculates bearings of lines with respect to magnetic needle.
In order to calculate the position line, the time of the sight must be known so that the celestial position i.e. the Greenwich Hour Angle (Celestial Longitude - measured in a westerly direction from Greenwich) and Declination (Celestial Latitude - measured north or south of the equational or celestial equator), of the observed celestial body is ...
Magnetic deviation is the angle from a given magnetic bearing to the related bearing mark of the compass. Deviation is positive if a compass bearing mark (e.g., compass north) is right of the related magnetic bearing (e.g., magnetic north) and vice versa.
The process of keeping track of where the ship was likely to be was called rangekeeping, because the distance to the target—the range—was a very important factor in aiming the guns accurately. As time passed, train (also called bearing), the direction to the target, also became part of rangekeeping, but tradition kept the term alive.
Diagram showing principle of constant bearing, decreasing range in marine collision avoidance. When an observer sees another vessel at a constant bearing and the range continually decreases, collision is imminent. A ship seen to be on a constant bearing with decreasing range will collide with the observer's ship unless avoiding action is taken.
Strike and dip are measured in the field using a compass and with a clinometer. A compass is used to measure the azimuth of the strike, and the clinometer measures inclination of the dip. [2] Dr. E. Clar first described the modern compass-clinometer in 1954, and some continue to be referred to as Clar compasses. [10]