This module is based on the specifications: ISO 19111 – Geographic information – Spatial Referencing by Coordinates and OGC - Implementation Specification: Coordinate Transformation Services and at providing the mechanisms to represent a coordinate that describes a position on or near the Earth's surface and are referenced to a model of the Earth. Coordinates are referenced to a Coordinate Reference System (CRS). A Coordinate Reference System is a Coordinate System (CS) – an abstract mathematical concept without any relationship to a physical object – that is referenced through a Datum to the Earth or some other object such as a vessel.

The SRS module offers this concepts, as classes of the namespace te::srs: including:SpatialReferenceSystem, GeographicCoordinateSystem,ProjectedCoordinateSystem, GeographicCoordinateSystem, Ellipsoid and Datum. Check the DOxygen documentation of this module, where these and other classes are documented in details.

In practice, users can describe an SRS in different ways:

• an arbitrary textual description (e.g. “UTM Zone 26S Datum WGS84”)
• a Well-known text representation of coordinate reference systems, from OGC
• an unique ID given by a responsible authority SRS Id and Authority responsible (e.g. EPSG 32726)
• a textual description as proposed by the PROJ.4 - Cartographic Projections Library (e.g. +proj=utm +zone=26 +south +ellps=WGS84 +datum=WGS84 +units=m +no_defs )

PROJ.4 descriptiosn it is not a OGC standard, PROJ.4 descriptions are used to represent SRS whenever PROJ.4 is used to perform transformations between two different SRS.

A Mananger is responsible for building SRS from textual representations identified by its types. The figure below shows the classes involved in this operation.