Nature: What is Latitude and Longitude?

By Robert K. Foster

Latitude

The Equator is a line around the Earth that is the same distance from both the North and South poles and is the Latitude line given a value of 0 degrees. There are 90 degrees of Latitude going both North and South from the Equator. All lines of Latitude are parallel to the Equator and are sometimes referred to as “Parallels”. Lines South of the Equator are given negative values if the direction name is omitted. Lines to the North are given positive values.

Longitude

Longitude lines, also called Meridians, are perpendicular to the lines of Latitude and run through both poles in what are called “great circles”. By international agreement, the meridian line through Greenwich, England, is currently given the value of 0 degrees of longitude; this meridian is referred to as the Prime Meridian.

The Earth is divided equally into 360 degrees of longitude. There are 180 degrees of longitude to the east of the Prime Meridian; when the directional designator is omitted these longitudes are given positive values. There are also 180 degrees of longitude to the west of the Prime Meridian; when the directional designator is omitted these longitudes are given negative values. The 180-degree longitude line is opposite the Prime Meridian on the globe, and is the same going either east or west.

Source: National Atlas, http://www.nationalatlas.gov/articles/mapping/a_latlong.html

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