Relative bearing
Encyclopedia
In nautical navigation
the relative bearing of an object is the clockwise angle in degree
s from the heading of the vessel to a straight line drawn from the observation station on the vessel to the object.
The relative bearing is measured with a pelorus
or other optical and electronic aids to navigation such as a periscope
, sonar system, and radar systems. Since World War II, relative bearings of such diverse point sources have been and are calibrated carefully to one another. The United States Navy
operates a special range off Puerto Rico
and another on the west coast to perform such systems integration. Relative bearings then serve as the baseline data for converting relative directional data into true bearings (N-S-E-W, relative to the Earth's true geography). By contrast, Compass bearings have a varying error factor at differing locations about the globe, and are less reliable than the compensated or true bearings.
The measurement of relative bearings of fixed landmarks and other navigational aid
s is useful for the navigator because this information can be used on the nautical chart
together with simple geometrical techniques to aid in determining the position of the vessel and/or its speed, course, etc.
The measurement of relative bearings of other vessels and objects in movement is useful to the navigator in avoiding the danger of collision.
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
the relative bearing of an object is the clockwise angle in degree
Degree (angle)
A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...
s from the heading of the vessel to a straight line drawn from the observation station on the vessel to the object.
The relative bearing is measured with a pelorus
Pelorus (instrument)
In appearance and use, a pelorus resembles a compass or compass repeater, with sighting vanes or a sighting telescope attached, but it has no directive properties. That is, it remains at any relative direction to which it is set. It is generally used by setting 000° at the lubber's line. Relative...
or other optical and electronic aids to navigation such as a periscope
Periscope
A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....
, sonar system, and radar systems. Since World War II, relative bearings of such diverse point sources have been and are calibrated carefully to one another. The United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
operates a special range off Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
and another on the west coast to perform such systems integration. Relative bearings then serve as the baseline data for converting relative directional data into true bearings (N-S-E-W, relative to the Earth's true geography). By contrast, Compass bearings have a varying error factor at differing locations about the globe, and are less reliable than the compensated or true bearings.
The measurement of relative bearings of fixed landmarks and other navigational aid
Navigational aid
A navigational aid is any sort of marker which aids the traveler in navigation; the term is most commonly used to refer to nautical or aviation travel...
s is useful for the navigator because this information can be used on the nautical chart
Nautical chart
A nautical chart is a graphic representation of a maritime area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land , natural features of the seabed, details of the coastline, navigational hazards, locations of natural and man-made aids...
together with simple geometrical techniques to aid in determining the position of the vessel and/or its speed, course, etc.
The measurement of relative bearings of other vessels and objects in movement is useful to the navigator in avoiding the danger of collision.
- Example: The navigator on a ship observes a lighthouse when its relative bearing is 45º and again when it is 90º. he now knows that the distance from the ship to the lighthouse is equal to the distance travelled by the vessel between both observations.