**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 arc degree of longitude. The distance around the Earth measures 360 degrees.**

The meridian that runs through Greenwich, England, is internationally accepted as the line of 0 degrees longitude, or prime meridian. The anti meridian is halfway around the world, at 180 degrees. It is the basis for the International Date Line.

Half of the world, the Eastern Hemisphere, is measured in degrees east of the prime meridian. The other half, the Western Hemisphere, in degrees west of the prime meridian.

Degrees of longitude are divided into 60 minutes. Each minute of longitude can be further divided into 60 seconds. For example, the longitude of India, is 78.87 18° E (78.87, 18 minutes east) and latitude is 21.76 79° N(21.76 degrees,79minutes North)

A degree of longitude is about 111 kilometers (69 miles) at its widest. The widest areas of longitude are near the Equator, where the Earth bulges out. Because of the Earth's curvature, the actual distance of a degrees, minutes, and seconds of longitude depends on its distance from the Equator. The greater the distance, the shorter the length between meridians. All meridians meet at the North and South Poles.

Longitude is related to latitude, the measurement of distance north or south of the Equator. Lines of latitude are called parallels. Maps are often marked with parallels and meridians, creating a grid. The point in the grid where parallels and meridians intersect is called a coordinate.Coordinates can be used to locate any point on Earth.

Knowing the exact coordinates of a site (degrees, minutes, and seconds of longitude and latitude) is valuable formilitary, engineering, and rescue operations. Coordinates can give military leaders the location of weapons or enemy troops. Coordinates help engineers plan the best spot for a building, bridge, well, or other structure. Coordinates help airplane pilots land planes or drop aid packages in specific locations.

**Latitude**

**is the measurement of distance north or south of the Equator. It is measured with 180 imaginary lines that form circles around the Earth east-west, parallel to the Equator. These lines are known as parallels. A circle of latitude is an imaginary ring linking all points sharing a parallel.**

The Equator is the line of 0 degrees latitude. Each parallel measures one degree north or south of the Equator, with 90 degrees north of the Equator and 90 degrees south of the Equator. The latitude of the North Pole is 90 degrees N, and the latitude of the South Pole is 90 degrees S.

Like the poles, some circles of latitude are named. The Tropic of Cancer, for instance, is 23 degrees 26 minutes 21 seconds N—23° 26' 21'' N. Its twin, the Tropic of Capricorn, is 23° 26' 21'' S. The tropics are important geographic locations that mark the northernmost and southernmost latitudes where the sun can be seen directly overhead during a solstice.

One degree of latitude, called an arcdegree, covers about 111 kilometers (69 miles). Because of the Earth'scurvature, the farther the circles are from the Equator, the smaller they are. At the North and South Poles, arcdegrees are simply points.

Degrees of latitude are divided into 60 minutes. To be even more precise, those minutes are divided into 60 seconds. One minute of latitude covers about 1.8 kilometers (1.1 miles) and one second of latitude covers about 32 meters (105 feet).

For example, the latitude for Cairo, Egypt, in degrees and minutes would be written as 29° 52' N, because the city is 29 degrees, 52 minutes north of the Equator. The latitude for Cape Town, South Africa, would be 33° 56' S, because the city is 33 degrees, 56 minutes south of the Equator. Using seconds of latitude, global positioning system (GPS)devices can pinpoint schools, houses, even rooms in either of these towns.

Similar to latitude, the corresponding measurement of distance around the Earth is called longitude. The imaginary lines of latitude and longitude intersect each other, forming a grid that covers the Earth. The points of latitude and longitude are called coordinates, and can be used together to locate any point on Earth.

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