A geographic coordinate system is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are often chosen such that one of the numbers represents a vertical position, and two or three of the numbers represent a horizontal position. A common choice of coordinates is latitude, longitude and elevation.To specify a location on a two-dimensional map requires a map projection. We place the geographic grid of parallels and meridians onto the map projection to be able to identify any location on the earth's surface.
The Geographic grid is a system of imaginary arcs drawn in a grid pattern on Earth’s surface.
–Meridians are arcs drawn between the North and South poles. Each is numbered, according to a system known as longitude.
Values range from 0º (prime meridian) to 180º east or west longitude.
–Parallels are arcs drawn parallel to the equator and at right angles to meridians. Each is numbered, according to a system known as latitude.
Values range from 0º (equator) to 90º north or south
- Here is a video that may help you visualize how these projected lines actually work.
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