Projected coordinate system

The term is used in international standards such as the EPSG and ISO 19111 (also published by the Open Geospatial Consortium as Abstract Specification 2), and in most geographic information system software.

[3][2] The map projection and the geographic coordinate system (GCS, latitude and longitude) date to the Hellenistic period, proliferating during the Enlightenment Era of the 18th century.

In the United Kingdom, the first version of the British National Grid was released in 1938, based on earlier experiments during World War I by the Army and the Ordnance Survey.

[6] To facilitate unambiguous reporting, the alphanumeric Military Grid Reference System (MGRS) was then created as an encoding scheme for UTM coordinates to make them easier to communicate.

Because UTM zones do not align with political boundaries, several countries followed the United Kingdom in creating their own national or regional grid systems based on custom projections.

GIS requires locations to be specified as precise coordinates and performs numerous calculations on them, making Cartesian geometry preferable to spherical trigonometry when computing power was at a premium.

In recent years, the rise of global GIS datasets and satellite navigation, along with an abundance of processing speed in personal computers, have led to a resurgence in the use of GCS.

Because the purpose of any coordinate system is to accurately and unambiguously measure, communicate, and perform calculations on locations, it must be defined precisely.

[7] Given the parameters associated with particular location or grin, the projection formulas for the transverse Mercator are a complex mix of algebraic and trigonometric functions.

[8] The grid lines on Ordnance Survey maps divide the UK into one-kilometre squares, east of an imaginary zero point in the Atlantic Ocean, west of Cornwall.

[9] Since the meridians converge at the poles, true east and west directions change rapidly in a condition similar to gimbal lock.

While such precise numbers are easy to store and calculate in GIS and other computer databases, they can be difficult for humans to remember and communicate.

[11] Alphanumeric encodings typically use codes to replace the most significant digits by partitioning the world up into large grid squares.

Grid references comprising larger numbers for greater precision could be determined using large-scale maps and an accurate Romer.

A GPS unit commonly gives a ten-digit grid reference, based on two groups of five numbers for the Easting and Northing values.