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The meridian 30° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Greenland, the Atlantic Ocean, the Southern Ocean, and Antarctica to the South Pole.
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While latitude is the angular distance to the north or south of the Equator (0°), longitude is the angular distance of a particular location to the east or west from the zero meridian. Search For Latitude & Longitude Map
- Overview
- A framework for describing locations
- Technical considerations
Latitude is a measurement on a globe or map of location north or south of the Equator. Technically, there are different kinds of latitude, which are geocentric, astronomical, and geographic (or geodetic), but there are only minor differences between them.
What is the length of a degree of latitude?
The length of a degree of arc of latitude is approximately 111 km (69 miles), varying, because of the nonuniformity of Earth’s curvature, from 110.567 km (68.706 miles) at the Equator to 111.699 km (69.41 miles) at the poles.
What is longitude?
Longitude is a measurement of location east or west of the prime meridian at Greenwich, London, England, the specially designated imaginary north-south line that passes through both geographic poles and Greenwich. Longitude is measured 180° both east and west of the prime meridian.
What is the distance per degree of longitude?
Lines of latitude (also called parallels) are imaginary lines that circle Earth’s surface, running east and west parallel to the Equator. Lines of longitude (also called meridians) run between the geographic North Pole and the geographic South Pole and are used to measure distances from the prime meridian. Both latitude and longitude are measured in degrees (°), which may be broken down into smaller units called minutes (′) and seconds (″). (Or they may be expressed in decimal degrees; negative values of decimal degrees represent latitudes in the Southern Hemisphere and longitudes in the Western Hemisphere.) The latitudes of the North Pole and South Pole are 90° north (N) and 90° south (S), respectively. Lines of latitude north of the Equator (the line that marks 0° latitude) are numbered from 1° to 89° N, and those south of the Equator are numbered from 1° to 89° S. Lines of longitude east of the prime meridian (the line that marks 0° longitude) are numbered from 1° to 179° east (E). Lines of longitude west of the prime meridian are numbered from 1° to 179° west (W). The 180th meridian, or 180°—which can be drawn north-south from pole to pole across the middle of the Pacific Ocean—is the line of longitude exactly opposite the prime meridian.
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The combination of meridians of longitude and parallels of latitude establishes a framework or grid that can be used to locate exact positions on a map or globe. For example, a point made up of the coordinates 40° N 30° W is located at latitude 40° north of the Equator and longitude 30° west of the Greenwich meridian (which is expressed in decimal degrees as latitude 40 and longitude –30). The location of Washington, D.C., which lies 39 degrees north of the Equator and 77 degrees west of the prime meridian, can be described using the coordinates 39° N 77° W. (In decimal degree formatting, the approximate location of Washington, D.C., is latitude 39 and longitude –77.)
Technically speaking, 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 (a curved line) that can be drawn along Earth’s surface, created by an imaginary plane that passes through Earth’s center, whose angle diverges from that of the equatorial plane (that is, the imaginary plane that cuts through Earth and includes all points along the Equator). Thus, a point at 30°15′20″ N is the arc that results from an angle of 30°15′20″ at the center of the globe. Astronomical latitude is the angle created by the equatorial plane and a line created by the direction of gravity (that is, the plumb line) occurring at a given point on Earth’s surface.
Geographic latitude, which is the kind used in mapping, is calculated using a slightly different process. Because Earth is not a perfect sphere—the planet’s curvature is flatter at the poles—geographic latitude is the arc resulting from an angle created by the equatorial plane and the normal line that can be drawn from a given point on Earth’s surface to Earth’s center. (The normal line is perpendicular to a tangent line touching Earth’s curvature at that point on the surface.) Different methods are used to determine geographic latitude, as by taking angle-sights on certain polar stars or by measuring with a sextant the angle of the noon Sun above the horizon. The length of a degree of arc of latitude is approximately 111 km (69 miles), varying, because of the nonuniformity of Earth’s curvature, from 110.567 km (68.703 miles) at the Equator to 111.699 km (69.41 miles) at the poles. Geographic latitude is also given in degrees, minutes, and seconds.
In contrast, longitude is the amount of arc created by drawing first a line from Earth’s center to the intersection of the Equator and the prime meridian and then another line drawn from Earth’s center to any point elsewhere along the Equator. Since lines of longitude are not parallel to one another, the distance between one degree of longitude and the next will vary significantly depending upon how close to the poles the measurement is taken. The distance per degree of longitude at the Equator is about 111.32 km (69.17 miles) and at the poles, 0.
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The four cardinal directions, or cardinal points, are the four main compass directions: north, south, east, and west, commonly denoted by their initials N, S, E, and W respectively. Relative to north, the directions east, south, and west are at 90 degree intervals in the clockwise direction.
Apr 9, 2019 · For example, 30°E, the line passing through eastern Africa, is an angular distance of 30° east of the Prime Meridian. 30°W, which is in the middle of the Atlantic Ocean, is an angular distance of 30° west of the Prime Meridian.
