SEW - Geographical Coordinate System Lesson

 

Geographical Coordinate System

Using the equator and the prime meridian as a constant, map makers have created a grid system called the geographic coordinate system (GCS). The geographic coordinate system uses a three-dimensional spherical surface to define locations on Earth. GCS uses longitude and latitude to find locations anywhere on Earth.

Latitude, the north and south distance from the equator is measured in degrees. All lines of latitude run parallel to the equator. The equator is 0, and Latitude is measured in ranges from +90° (or 90° N) at the North pole to -90° (or 90° S) at the South pole. A line of latitude is also known as a parallel.

Longitude, the east and west distance from the prime meridian is also measured in degrees. There are 360 lines of longitude that run from north to south converging at the poles. Each line represents one degree of longitude. The prime meridian measures 0°, and Longitude measures   +180 (or 180° E) to -180° (or 180° W). The 180° east or west is one half the total number of degrees in a circle.

The common practice is to report GCS with the latitude first and then the longitude value separated by a comma. The GCS coordinates of Atlanta, Georgia are 33.7490° N, 84.3880° W. There are several ways that you can indicate direction. For the latitude coordinate, you may see an indication of the direction from the equator by using the '-' symbols or S (degrees South). For longitude, the direction of the prime meridian, you might see the minus symbol or W (degrees West).