False origin

The origin of a grid is a fixed point from where measurements are taken, typically found at the x, y coordinates (0,0). In regards to map projections, a false origin is an adjustment of that original origin at (0,0) to a different location either east or north of the zone from which measurements are being taken. In moving the origin to the east or west, all values of latitude and longitude then become positive; thus avoiding errors in map calculations. The location shift or value added to the x-coordinate is known as the false easting. The shift or value added to the y-coordinate is known as the false northing.

By using a false origin the reader of a map may more easily locate specific points on the map through avoiding the use of negative numbers.

Cartographic Uses
A false origin is most commonly used with UTM coordinate system, but it is also used with others systems such as the State Plane Coordinate System. For the UTM coordinate system, false easting is 500,000 meters. The false northing depends on whether the point is in the Northern or Southern Hemisphere. If the point is in the Northern Hemisphere, it has a false northing of 0 while a point in the Southern Hemisphere has a false northing of 10,000,000 meters.

In the State Plate Coordinate System, a false origin is placed outside of the area it covers and serves as a common reference point for surveyors and cartographers. Some states have one coordinate system for their entire territory such as Tennessee and Montana. In cases where a state has separate coordinate systems for different parts of their territory, each coordinate system will be assigned its own false origin.

False origins and plane coordinates are only useful on large-scale maps. On small-scale maps the distortions that result from projecting the surface of the earth to a plane make it difficult to use to run calculations or position phenomena. In the United States, large-scale topographic maps usually include at least one system of plane coordinates. For example, the 1:24,000-scale topographic maps will have markings for various grid systems that indicate how far features are from the false origin or meridian.