Position line
Encyclopedia
A position line is a line that can be identified both on a nautical chart
or aeronautical chart
and by observation out on the surface of the earth
. The intersection of two position lines is a fix
that is used in position fixing
to identify the navigator's location.
There are several types of position line:
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...
or aeronautical chart
Aeronautical chart
An aeronautical chart is a map designed to assist in navigation of aircraft, much as nautical charts do for watercraft, or a roadmap for drivers...
and by observation out on the surface of the earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. The intersection of two position lines is a fix
Fix (position)
In position fixing navigation, a position fix or simply a fix is a position derived from measuring external reference points.The term is generally used with manual or visual techniques such as the use of intersecting visual or radio position lines rather than the use of more automated and accurate...
that is used in position fixing
Position fixing
Position fixing is the branch of navigation concerned with the use of a variety of visual and electronic methods to determine the position of a ship, aircraft or person on the surface of the Earth.These techniques include:...
to identify the navigator's location.
There are several types of position line:
- CompassCompassA compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...
bearingBearing (navigation)In marine navigation, a bearing is the direction one object is from another object, usually, the direction of an object from one's own vessel. In aircraft navigation, a bearing is the actual compass direction of the forward course of the aircraft...
- the angleAngleIn geometry, an angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle.Angles are usually presumed to be in a Euclidean plane with the circle taken for standard with regard to direction. In fact, an angle is frequently viewed as a measure of an circular arc...
between northNorthNorth is a noun, adjective, or adverb indicating direction or geography.North is one of the four cardinal directions or compass points. It is the opposite of south and is perpendicular to east and west.By convention, the top side of a map is north....
and the line passing through the compass and the point of interest - TransitNavigational transitIn navigation and position fixing, a transit occurs when a navigator observes two fixed reference points that are in line with the navigator. This creates a position line...
- a line passing through the observer and two other reference points - Leading lineLeading lineA leading line, called a "range" in the United States, is a line formed by a pair of marks, which are generally man-made, that are used in position fixing and navigation, to indicate a safe passage through a shallow or dangerous channel...
- the line passing through two marks indicating a safe channel - Leading lightsLeading lightsLeading lights are a pair of light beacons, used in navigation to indicate a safe passage for vessels entering a shallow or dangerous channel; and may also be used for position fixing. At night, the lights are a form of leading line that can be used for safe navigation...
- the line passing through two beacons indicating a safe channel - Sector lightsSector lightsSector lights are a man-made pilotage and position fixing aid that consist of strictly de-limited horizontal angle light beams to guide water-borne traffic through a safe channel at night in reasonable visibility. They are most often used for safe passage through shallow or dangerous waters. This...
– the lines created by masked coloured lights that indicate a safe channel
See also
- NavigationNavigationNavigation 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...
- Position circlePosition circleA position circle is a circle that can be measured both from a chart and from the surface of the earth for the purpose of position fixing. The circles can be measured by sextant. Two overlapping position circles can be used to give a position fix.-See also:...