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What are latitude and longitude and how do they relate to GIS?

To display an accurate visual representation of a location, a GIS uses an absolute location reference system. Latitude and longitude, written in degrees (°), is one such system.

Latitude lines, known as parallels, run horizontally, and measure the distance north or south of the Equator. The Equator is the starting point of measuring latitude and is 0° latitude. Latitude is measured in degrees from 0° to 90° and is specified as North or South.

Longitude lines run vertical and are known as meridians. They indicate the distance east or west of the "prime meridian." The prime meridian runs through Greenwich, England and is 0°longitude.