Coordinate Systems

The Web Mercator projection uses a modified version of the Mercator projection and has become a default map projection for web mapping.

The central meridian is the center line of longitude for projection systems. Projected coordinate systems often use it as a reference point for a x-origin.

Latitude lines run east-west, are parallel and go from -90 to +90. Longitude lines run north-south, converge at the poles and are from -180 to +180.

The State Plane Coordinate System divides the United States into 124 zones to locate any point with a high level of accuracy (one part in 10,000).

Universal Transverse Mercator (UTM) segments the Earth into 60 zones (each UTM zone is 6‎°) and projects each zone with an upright cylinder of its own.

Ellipsoids, survey benchmarks and triangulation – these are the ingredients for geodetic datums. NAD27, NAD83 and WGS84 are common datums in North America.

We can find any location on Earth using latitude and longitude coordinates. And we measure those coordinates with decimal degrees or degrees/minutes/seconds

The Greenwich Meridian (or Prime Meridian) is a zero degrees longitudinal It is the start-point which we measure 180 degrees east and west.

North American Datum of 1983 (NAD83) is 2-meters from geocentric and uses thousands of monuments with triangulation to create a reference frame for Earth

The World Geodetic System 1984 (WGS84) is the spatial reference system of GPS satellites with an error of less than 2 centimeters to the center of Earth.