Coordinate system Topic 2 - Spatial referencing by coordinates
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Copyright © 2010 Open Geospatial Consortium, Inc.
In this Abstract Specification, coordinate systems shall be divided into subtypes by the geometric properties of the coordinate space spanned and the geometric properties of the
axes themselves straight or curved; perpendicular or not. Certain subtypes of coordinate system shall be used only with specific subtypes of coordinate reference system as shown
in the UML class diagram in Figure 8 and Table 15. For derived CRSs, the constraints on CS association shall be by derived CRS subtype and follow the constraints for the
equivalent subtype of principle CRS.
A description of coordinate system subtypes is included in Table 15.
This Abstract Specification additionally allows for user-defined coordinate systems. Each of these shall be used with one of the coordinate reference system subtypes described in
Clause 8.
Table 15 — Subtypes of coordinate system and constraints in its relationship with coordinate reference system
CS subtype Description
Used with CRS types
affine two- or three-dimensional coordinate system with straight axes that are not necessarily
orthogonal. Engineering
Image Cartesian
two- or three-dimensional coordinate system which gives the position of points relative to orthogonal straight axes. All axes shall have the same unit of measure.
Geodetic Projected
Engineering Image
cylindrical three-dimensional coordinate system consisting of a polar coordinate system extended by a
straight coordinate axis perpendicular to the plane spanned by the polar coordinate system. Engineering
ellipsoidal two- or three-dimensional coordinate system in which position is specified by geodetic
latitude, geodetic longitude and in the three-dimensional case ellipsoidal height. Geodetic
linear one-dimensional coordinate system that consists of the points that lie on the single axis
described. Example: usage of the line feature representing a pipeline to describe points on or along that pipeline.
This Abstract Specification only lends itself to be used for simple =continuous linear systems. For a more extensive treatment of the subject, particularly as applied to the
transportation industry, refer to ISO 19133 [7]. Engineering
polar two-dimensional coordinate system in which position is specified by distance from the
origin and the angle between the line from origin to point and a reference direction. Engineering
spherical three-dimensional coordinate system with one distance, measured from the origin, and two
angular coordinates. Not to be confused with an ellipsoidal coordinate system based on an ellipsoid ‘degenerated’ into a sphere.
Geodetic Engineering
vertical one-dimensional coordinate system used to record the heights or depths of points
dependent on the Earth’s gravity field. An exact definition is deliberately not provided as the complexities of the subject fall outside the scope of this specification.
Vertical
Coordinate systems are described further in B.2.1.