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Subject: RE: ISO Definitions for corodinate, coordinate system, etc.

All -

The following are terms and definitions from ISO 19111 - Spatial Referencing by Coordinates and the OGC Abstract Specification, Topic 2: Spatial Referencing by Coordinates. Use as necessary. The normative reference would be:

ISO 19111, Geographic Information Spatial Referencing by Coordinates



Terms and definitions

For the purposes of this document, the following terms and definitions apply. Some definitions deviate from ISO/DIS 19111, where more universally valid definitions are provided.


Cartesian coordinate system

coordinate system which gives the position of points relative to N mutually-perpendicular straight axes

NOTE In the context of geospatial coordinates the maximum value of N is three.


compound coordinate reference system

coordinate system describing the position of points through two or more independent coordinate reference systems

EXAMPLE One coordinate reference system can be a two-dimensional horizontal coordinate system, and the other coordinate reference system can be a vertical gravity-related height system.


concatenated transformation

sequential application of multiple transformations



one of a sequence of N numbers designating the position of a point in N-dimensional space

NOTE In a coordinate reference system, the coordinate numbers must be qualified by units.

OGC 03-073r1

OGC 2003 All rights reserved 3


coordinate conversion

change of coordinates, based on a one-to-one relationship, from one coordinate reference

system to another based on the same datum

EXAMPLE Between geodetic and Cartesian coordinate systems or between geodetic coordinates and projected

coordinates, or change of units such as from radians to degrees or feet to metres.

NOTE A conversion uses parameters which have specified values, not empirically determined values.


coordinate reference system

coordinate system which is related to the real world by a datum

NOTE For geodetic and vertical datums, it will be related to the Earth.


coordinate system

set of (mathematical) rules for specifying how coordinates are to be assigned to points

NOTE 1 One coordinate system may be used in many coordinate reference systems.

NOTE 2 The geometric properties of a coordinate space determine how distances and angles between

points are calculated from the coordinates. For example, in an ellipsoidal (2D) space distances are defined

as curves on the surface of the ellipsoid, whereas in a Euclidean plane as used for projected CRS distance is

the length of a straight line between two points. The mathematical rules that determine distances and angles

are calculated from coordinates and vice versa are comprised in the concept of coordinate system.

Carl Reed, PhD
CTO and Executive Director Specification Program

The OGC: Helping the World to Communicate Geographically
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