# Geographical coordinates

## Geographic coordinates

Spherical angular coordinate reference system to represent locations on earth. At least three values will be needed to represent a location: one for the horizontal position, one for the vertical position, and a third indicating the distance to ground level, which is identified as sea level. The values of horizontal and vertical position are usually given in sexagesimal degrees, since these are angles whose center is the Earth.

## Meridians and parallels

The terrestrial sphere is divided with imaginary lines called **meridians** and **parallels** .

### Meridians

Meridians are lines that run from the North Pole to the South Pole. The prime meridian, zero meridian or Greenwich meridian is the imaginary line that joins the north and south poles passing through the town of Greenwich in England, the rest of the meridians take this as a reference. To the east the meridians are taking positive values up to 180º while to the west the values taken are negative.

### Parallels

Parallels are lines from east to west, are perpendicular to the north-south axis and are parallel to the Equator. The equator is parallel "0".

## Latitude y Longitude

### Latitude

The **latitude** of a point on the earth's surface is the angle between the plane passing through the equator and the line passing through the point and the center of the earth. All points with the same latitude form imaginary circles that are "parallel" to each other and parallel to the equator, which is the larger of the "parallels."

### Longitude

The **longitude** of a point on the earth's surface is the angle between the plane passing through the Greenwich meridian and the plane of the meridian passing through the point. All points with the same length form semicircles that pass through the poles similar to the segments of an orange.

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