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Spatial reference system

A spatial reference system (SRS) or coordinate reference system (CRS) is a framework used to precisely measure locations on the surface of Earth as coordinates. It is thus the application of the abstract mathematics of coordinate systems and analytic geometry to geographic space. A particular SRS specification (for example, "Universal Transverse Mercator WGS 84 Zone 16N") comprises a choice of Earth ellipsoid, horizontal datum, map projection (except in the geographic coordinate system), origin point, and unit of measure. Thousands of coordinate systems have been specified for use around the world or in specific regions and for various purposes, necessitating transformations between different SRS.

"SRID" redirects here. For the polyhedron, see Rhombicosidodecahedron.

Although they date to the Hellenic Period, spatial reference systems are now a crucial basis for the sciences and technologies of Geoinformatics, including cartography, geographic information systems, surveying, remote sensing, and civil engineering. This has led to their standardization in international specifications such as the EPSG codes[1] and ISO 19111:2019 Geographic information—Spatial referencing by coordinates, prepared by ISO/TC 211, also published by the Open Geospatial Consortium as Abstract Specification, Topic 2: Spatial referencing by coordinate.[2]

A , an abstract framework for measuring locations. Like any mathematical coordinate system, its definition consists of a measurable space (whether a plane, a three-dimension void, or the surface of an object such as the Earth), an origin point, a set of axis vectors emanating from the origin, and a unit of measure.

coordinate system

A , which binds the abstract coordinate system to the real space of the Earth. A horizontal datum can be defined as a precise reference framework for measuring geographic coordinates (latitude and longitude). Examples include the World Geodetic System and the 1927 and 1983 North American Datum. A datum generally consists of an estimate of the shape of the Earth (usually an ellipsoid), and one or more anchor points or control points, established locations (often marked by physical monuments) for which the measurement is documented.

horizontal datum

A definition for a projected CRS must also include a choice of to convert the spherical coordinates specified by the datum into cartesian coordinates on a planar surface.

map projection

The goal of any spatial reference system is to create a common reference frame in which locations can be measured precisely and consistently as coordinates, which can then be shared unambiguously, so that any recipient can identify the same location that was originally intended by the originator.[3] To accomplish this, any coordinate reference system definition needs to be composed of several specifications:


Thus, a CRS definition will typically consist of a "stack" of dependent specifications, as exemplified in the following table:

China

Chinese Global Navigation Grid Code

Israel

Israeli Cassini Soldner

Israel

Israeli Transverse Mercator

Jordan

Jordan Transverse Mercator

Engineering datum

Geodesy

Geodetic datum

Georeferencing

Geographic coordinate systems

(GIS).

Geographic information system

Grid reference

Linear referencing

List of National Coordinate Reference Systems

Terms of orientation

– A website with more than 13000 spatial reference systems, in a variety of formats.

spatialreference.org

Archived 2004-12-13 at the Wayback Machine

OpenGIS Specifications (Standards)

OpenGIS Simple Features Specification for CORBA (99-054)

OpenGIS Simple Features Specification for OLE/COM (99-050)

OpenGIS Simple Features Specification for SQL (99-054, 05-134, 06-104r3)

Archived 2006-04-22 at the Wayback Machine — library implementing relevant OGC standards

OGR

- Official EPSG Geodetic Parameter Dataset webpage. Search engine for EPSG defined reference systems.

EPSG.org

- Full text search indexing over 6000 coordinate systems

EPSG.io/

Galdos Systems INdicio CRS Registry