northing

Northing is a coordinate used in map projections and grid reference systems to indicate how far a point lies northward, measured along a north-south axis. It represents a linear distance, typically in meters or feet, rather than an angular value like latitude. In many coordinate systems, northing is the second component of a two-number grid reference alongside easting, which measures east–west position.

In projected coordinate systems, the surface of the earth is transformed onto a plane, producing two axes: easting (eastward distance) and northing (northward distance). Northing increases as one moves north, and false northings are commonly applied to avoid negative values near the equator or in the lower latitudes of a zone. Converting between geographic coordinates (latitude and longitude) and projected coordinates requires a mathematical projection.

Common systems that use northing include the Universal Transverse Mercator (UTM) grid, the British National Grid (Ordnance Survey grid), and various State Plane and national grids. For example, in UTM, the northing value is measured in meters from the equator in the northern hemisphere, while southern hemisphere coordinates include a false northing of 10,000,000 meters at the equator so that values remain positive.

Northing is essential for precise location plotting, distance measurement, and GIS data analysis. When reading coordinates, it is important to know the reference system and units, as the same numeric pair can refer to different locations in different projections. Converting between projected coordinates and latitude–longitude requires inverse projection formulas from a defined datum.