Longitude
A Longitude is a geographical coodinate that specifies east-west position of point on Earth surface.
- Context:
- It can be recoded in a Toponym Record.
- Example(s):
Name="London", Longitude="81.24°W", Latitude="42.97°N"
- Counter-Example(s):
- See: Earth, Coordinate System, Location.
References
2018a
- (Wikipedia, 2018) ⇒ https://en.wikipedia.org/wiki/Longitude Retrieved:2018-11-4.
- Longitude, [1] is a geographic coordinate that specifies the east–west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians (lines running from pole to pole) connect points with the same longitude. By convention, one of these, the Prime Meridian, which passes through the Royal Observatory, Greenwich, England, was allocated the position of 0° longitude. The longitude of other places is measured as the angle east or west from the Prime Meridian, ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Specifically, it is the angle between a plane through the Prime Meridian and a plane through both poles and the location in question. (This forms a right-handed coordinate system with the -axis (right hand thumb) pointing from the Earth's center toward the North Pole and the -axis (right hand index finger) extending from the Earth's center through the Equator at the Prime Meridian.)
A location's north–south position along a meridian is given by its latitude, which is approximately the angle between the local vertical and the equatorial plane.
If the Earth were perfectly spherical and radially homogeneous, then the longitude at a point would be equal to the angle between a vertical north–south plane through that point and the plane of the Greenwich meridian. Everywhere on Earth the vertical north–south plane would contain the Earth's axis. But the Earth is not radially homogeneous and has rugged terrain, which affect gravity and so can shift the vertical plane away from the Earth's axis. The vertical north–south plane still intersects the plane of the Greenwich meridian at some angle; that angle is the astronomical longitude, calculated from star observations. The longitude shown on maps and GPS devices is the angle between the Greenwich plane and a not-quite-vertical plane through the point; the not-quite-vertical plane is perpendicular to the surface of the spheroid chosen to approximate the Earth's sea-level surface, rather than perpendicular to the sea-level surface itself.
- Longitude, [1] is a geographic coordinate that specifies the east–west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians (lines running from pole to pole) connect points with the same longitude. By convention, one of these, the Prime Meridian, which passes through the Royal Observatory, Greenwich, England, was allocated the position of 0° longitude. The longitude of other places is measured as the angle east or west from the Prime Meridian, ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Specifically, it is the angle between a plane through the Prime Meridian and a plane through both poles and the location in question. (This forms a right-handed coordinate system with the -axis (right hand thumb) pointing from the Earth's center toward the North Pole and the -axis (right hand index finger) extending from the Earth's center through the Equator at the Prime Meridian.)
2018b
- (NASA, 2018) ⇒ https://www.nasa.gov/audience/forstudents/k-4/dictionary/Longitude.html Retrieved:2018-11-4.
- QUOTE: a measurement of distance, given in degrees east or west of the prime meridian. The prime meridian is a line that runs through the Greenwich Observatory in London, England. On a map or globe, lines of longitude are drawn from the North Pole to the South Pole.
2018c
- (National Geographic, 2018) ⇒ https://www.nationalgeographic.org/encyclopedia/longitude/ Retrieved:2018-11-4.
- QUOTE: Longitude is the measurement east or west of the prime meridian. Longitude is measured by imaginary lines that run around the Earth vertically (up and down) and meet at the North and South Poles. These lines are known as meridians. Each meridian measures one arcdegree of longitude. The distance around the Earth measures 360 degrees.
2018d
- (Encyclopedia Britannica, 2018) ⇒ https://www.britannica.com/science/latitude#ref285656 Retrieved:2018-11-4.
- QUOTE: Latitude and longitude, coordinate system by means of which the position or location of any place on Earth’s surface can be determined and described. Latitude is a measurement on a globe or map of location north or south of the Equator. Technically, there are different kinds of latitude—geocentric, astronomical, and geographic (or geodetic)—but there are only minor differences between them. In most common references, geocentric latitude is implied. Given in degrees, minutes, and seconds, geocentric latitude is the arc subtended by an angle at Earth’s centre and measured in a north-south plane poleward from the Equator.