# Spatial reference system > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Spatial_reference_system > Markdown URL: https://mediated.wiki/source/Spatial_reference_system.md > Source: https://en.wikipedia.org/wiki/Spatial_reference_system > Source revision: 1336385139 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) System to specify locations on Earth Geodesy Fundamentals Geodesy Geodynamics Geomatics History Concepts Geographical distance Geoid Figure of the Earth (radius and circumference) Geodetic coordinates Geodetic datum Geodesic Horizontal position representation Latitude / Longitude Map projection Reference ellipsoid Satellite geodesy Spatial reference system Spatial relations Vertical positions Technologies Global Nav. Sat. Systems (GNSSs) Global Pos. System (GPS) GLONASS (Russia) BeiDou (BDS) (China) Galileo (Europe) NAVIC (India) Quasi-Zenith Sat. Sys. (QZSS) (Japan) Discrete Global Grid and Geocoding Standards (history) NGVD 29 Sea Level Datum 1929 OSGB36 Ordnance Survey Great Britain 1936 SK-42 Systema Koordinat 1942 goda ED50 European Datum 1950 SAD69 South American Datum 1969 GRS 80 Geodetic Reference System 1980 ISO 6709 Geographic point coord. 1983 NAD 83 North American Datum 1983 WGS 84 World Geodetic System 1984 NAVD 88 N. American Vertical Datum 1988 ETRS89 European Terrestrial Ref. Sys. 1989 GCJ-02 Chinese obfuscated datum 2002 Geo URI Internet link to a point 2010 International Terrestrial Reference System Spatial Reference System Identifier (SRID) Universal Transverse Mercator (UTM) v t e A **spatial reference system** (**SRS**) or **coordinate reference system** (**CRS**) is a framework used to precisely measure locations on, or relative to, the surface of Earth as coordinates. It is thus the application of the abstract mathematics of [coordinate systems](/source/Coordinate_system) and [analytic geometry](/source/Analytic_geometry) to geographic space. A particular SRS specification (for example, "[Universal Transverse Mercator](/source/Universal_Transverse_Mercator) [WGS 84](/source/WGS_84) Zone 16N") comprises a choice of [Earth ellipsoid](/source/Earth_ellipsoid), [horizontal datum](/source/Geodetic_datum), [map projection](/source/Map_projection) (except in the [geographic coordinate system](/source/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](/source/Geographic_coordinate_conversion) between different SRS. Although they date to the [Hellenistic period](/source/Hellenistic_period), spatial reference systems are now a crucial basis for the sciences and technologies of [Geoinformatics](/source/Geoinformatics), including [cartography](/source/Cartography), [geographic information systems](/source/Geographic_information_systems), [surveying](/source/Surveying), [remote sensing](/source/Remote_sensing), and [civil engineering](/source/Civil_engineering). This has led to their standardization in international specifications such as the [EPSG codes](/source/EPSG_code)[1] and *ISO 19111:2019 Geographic information—Spatial referencing by coordinates*, prepared by [ISO/TC 211](/source/ISO%2FTC_211), also published by the [Open Geospatial Consortium](/source/Open_Geospatial_Consortium) as *Abstract Specification, Topic 2: Spatial referencing by coordinate*.[2] The above refers to locations directly on the surface of the earth. Information on elevation may also be specified, via a vertical reference frame, so-called vertical CRS, or an integrated 3D CRS. Terminology in this area is evolving in line with increasing technical sophistication in measurement. ## Types of systems Earth centered, Earth fixed coordinates in relation to latitude and longitude. The thousands of spatial reference systems used today are based on a few general strategies, which have been defined in the EPSG, ISO, and OGC standards:[1][2] **[Geographic coordinate system](/source/Geographic_coordinate_system) (or geodetic)** - A [spherical coordinate system](/source/Spherical_coordinate_system) measuring locations directly on the Earth (modeled as a [sphere](/source/Sphere) or [ellipsoid](https://en.wikipedia.org/w/index.php?title=Geographic_ellipsoid&action=edit&redlink=1)) using [latitude](/source/Latitude) (degrees north or south of the [equator](/source/Equator)) and [longitude](/source/Longitude) (degrees west or east of a [prime meridian](/source/Prime_meridian)). **[Geocentric coordinate system](/source/Geocentric_coordinate_system) (or Earth-centered Earth-fixed)** - A three-dimensional [cartesian coordinate system](/source/Cartesian_coordinate_system) that models the Earth as a three-dimensional object, measuring locations from a center point, usually the [center of mass](/source/Center_of_mass) of the Earth, along x, y, and z axes aligned with the [equator](/source/Equator) and the [prime meridian](/source/Prime_meridian). This system is commonly used to track the orbits of [satellites](/source/Satellite), because they are based on the center of mass. Thus, this is the internal coordinate system used by [Satellite navigation](/source/Satellite_navigation) systems such as [GPS](/source/Global_Positioning_System) to compute locations using [multilateration](/source/True-range_multilateration). **[Projected coordinate system](/source/Projected_coordinate_system) (or planar, grid) Layout of a UTM coordinate system** - A standardized [cartesian coordinate system](/source/Cartesian_coordinate_system) that models the surface of Earth (or more commonly, a large region thereof) as a plane, measuring locations from an arbitrary origin point along x and y axes more or less aligned with the cardinal directions. Each of these systems is based on a particular [map projection](/source/Map_projection) to create a planar surface from the curved Earth surface. Such SRSs are generally defined and used strategically in their target regions to minimize the distortions inherent to projections for specific use cases. Common examples include the [Universal transverse mercator](/source/Universal_transverse_mercator) (UTM) and national systems such as the [British National Grid](/source/Ordnance_Survey_National_Grid), and [State Plane Coordinate System](/source/State_Plane_Coordinate_System) (SPCS). **Engineering coordinate system (or local, custom)** - A [cartesian coordinate system](/source/Cartesian_coordinate_system) (2-D or 3-D) that is created bespoke for a small area, often a single engineering project, over which the curvature of the Earth can be safely approximated as flat without significant distortion. Locations are typically measured directly from an arbitrary origin point using [surveying](/source/Surveying) techniques. These may or may not be aligned with a standard projected coordinate system. [Local tangent plane coordinates](/source/Local_tangent_plane_coordinates) are a type of local coordinate system used in aviation and marine vehicles. **Vertical reference frame** - A standard reference system for measuring [elevation](/source/Elevation) using [vertical datums](/source/Vertical_datum), based on [levelling](/source/Levelling), a [geoid](/source/Geoid) model, or a [chart datum](/source/Chart_datum) (considering [tides](/source/Tides)). This does not carry information about localization of a point on the surface of the earth, but elevation relative to the surface of the earth, importantly including specification of what zero elevation is. **3D (compound) coordinate system** - Combines a geographic or projected coordinate system with a vertical reference frame to provide a full parametrization of locations on or near the surface of the earth relative to a chosen zero elevation level. These standards acknowledge that standard reference systems also exist for [time](/source/Calendar_date) (e.g. [ISO 8601](/source/ISO_8601)). These may be combined with a spatial reference system to form a *compound coordinate system* for representing three-dimensional and/or spatio-temporal locations. There are also internal systems for measuring location within the context of an object, such as the rows and columns of pixels in a [raster image](/source/Raster_graphics), [Linear referencing](/source/Linear_referencing) measurements along linear features (e.g., highway mileposts), and systems for specifying location within moving objects such as ships. The latter two are often classified as subcategories of engineering coordinate systems. ## Components 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: - A [coordinate system](/source/Coordinate_system), 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. - A [geodetic datum](/source/Geodetic_datum) (horizontal, vertical, or three-dimensional) 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](/source/Geographic_coordinate_system) (latitude and longitude). Examples include the [World Geodetic System](/source/World_Geodetic_System) and the 1927 and 1983 [North American Datum](/source/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. - A definition for a projected CRS must also include a choice of [map projection](/source/Map_projection) to convert the spherical coordinates specified by the datum into cartesian coordinates on a planar surface. Thus, a CRS definition will typically consist of a "stack" of dependent specifications, as exemplified in the following table: EPSG code Name Ellipsoid Horizontal datum CS type Projection Origin Axes Unit of measure 4326 GCS WGS 84 GRS 80 WGS 84 ellipsoidal (lat, lon) —N/a equator/prime meridian equator, prime meridian degree of arc 26717 UTM Zone 17N NAD 27 Clarke 1866 NAD 27 cartesian (x,y) Transverse Mercator: central meridian 81°W, scaled 0.9996 500 km west of (81°W, 0°N) equator, 81°W meridian metre 6576 SPCS Tennessee Zone NAD 83 (2011) ftUS GRS 80 NAD 83 (2011 epoch) cartesian (x,y) Lambert Conformal Conic: center 86°W, 34°20'N, standard parallels 35°15'N, 36°25'N 600 km grid west of center point grid east at center point, 86°W meridian US survey foot ## Examples by continent Examples of systems around the world are: ### Asia - [Chinese Global Navigation Grid Code](/source/Global_Navigation_Grid_Code), China - [Israeli Cassini Soldner](/source/Israeli_Cassini_Soldner), Israel - [Israeli Transverse Mercator](/source/Israeli_Transverse_Mercator), Israel - [Jordan Transverse Mercator](/source/Jordan_Transverse_Mercator), Jordan ### Europe - [British national grid reference system](/source/British_national_grid_reference_system), Britain - Lambert-93 [(fr)](https://fr.wikipedia.org/wiki/Projection_conique_conforme_de_Lambert), the official projection in [Metropolitan France](/source/Metropolitan_France) - [Hellenic Geodetic Reference System 1987](/source/Hellenic_Geodetic_Reference_System_1987), Greece - [Irish grid reference system](/source/Irish_grid_reference_system), Ireland - [Irish Transverse Mercator](/source/Irish_Transverse_Mercator), Ireland - SWEREF 99 [(sv)](https://sv.wikipedia.org/wiki/SWEREF_99), Sweden ### North America - [United States National Grid](/source/United_States_National_Grid) and [State Plane Coordinate System](/source/State_Plane_Coordinate_System) (SPCS), US - [Modified transverse Mercator](/source/Modified_transverse_Mercator) coordinate system, Canada ### Worldwide - [Universal Transverse Mercator coordinate system](/source/Universal_Transverse_Mercator_coordinate_system) - [Lambert conformal conic projection](/source/Lambert_conformal_conic_projection) - [International mapcode system](/source/MapCode) - [Military Grid Reference System](/source/Military_Grid_Reference_System) ## Identifiers "SRID" redirects here. For the polyhedron, see [Rhombicosidodecahedron](/source/Rhombicosidodecahedron). A **Spatial Reference System Identifier** (**SRID**) is a unique value used to unambiguously identify projected, unprojected, and local spatial coordinate system definitions. These coordinate systems form the heart of all [GIS](/source/Geographic_information_system) applications. Virtually all major spatial vendors have created their own SRID implementation or refer to those of an authority, such as the [EPSG Geodetic Parameter Dataset](/source/EPSG_Geodetic_Parameter_Dataset). SRIDs are the primary key for the [Open Geospatial Consortium (OGC)](/source/Open_Geospatial_Consortium) **spatial_ref_sys** metadata table for the [Simple Features for SQL Specification, Versions 1.1 and 1.2](/source/Simple_Features), which is defined as follows: CREATE TABLE SPATIAL_REF_SYS ( SRID INTEGER NOT NULL PRIMARY KEY, AUTH_NAME CHARACTER VARYING(256), AUTH_SRID INTEGER, SRTEXT CHARACTER VARYING(2048) ) In spatially enabled databases (such as [IBM Db2](/source/IBM_Db2), [IBM Informix](/source/IBM_Informix), [Ingres](/source/Ingres_(database)), [Microsoft SQL Server](/source/Microsoft_SQL_Server), [MonetDB](/source/MonetDB), [MySQL](/source/MySQL), [Oracle RDBMS](/source/Oracle_RDBMS), [Teradata](/source/Teradata), [PostGIS](/source/PostGIS), [SQL Anywhere](/source/SQL_Anywhere) and [Vertica](/source/Vertica)), SRIDs are used to uniquely identify the coordinate systems used to define columns of spatial data or individual spatial objects in a spatial column (depending on the spatial implementation). SRIDs are typically associated with a [well-known text](/source/Well-known_text_representation_of_coordinate_reference_systems) (WKT) string definition of the coordinate system (SRTEXT, above). Here are two common coordinate systems with their EPSG SRID value followed by their WKT: UTM, Zone 17N, NAD27 — SRID 2029: PROJCS["NAD27(76) / UTM zone 17N", GEOGCS["NAD27(76)", DATUM["North_American_Datum_1927_1976", SPHEROID["Clarke 1866",6378206.4,294.9786982138982, AUTHORITY["EPSG","7008"]], AUTHORITY["EPSG","6608"]], PRIMEM["Greenwich",0, AUTHORITY["EPSG","8901"]], UNIT["degree",0.01745329251994328, AUTHORITY["EPSG","9122"]], AUTHORITY["EPSG","4608"]], UNIT["metre",1, AUTHORITY["EPSG","9001"]], PROJECTION["Transverse_Mercator"], PARAMETER["latitude_of_origin",0], PARAMETER["central_meridian",-81], PARAMETER["scale_factor",0.9996], PARAMETER["false_easting",500000], PARAMETER["false_northing",0], AUTHORITY["EPSG","2029"], AXIS["Easting",EAST], AXIS["Northing",NORTH]] [WGS84](/source/WGS84) — SRID 4326 GEOGCS["WGS 84", DATUM["WGS_1984", SPHEROID["WGS 84",6378137,298.257223563, AUTHORITY["EPSG","7030"]], AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0, AUTHORITY["EPSG","8901"]], UNIT["degree",0.01745329251994328, AUTHORITY["EPSG","9122"]], AUTHORITY["EPSG","4326"]] SRID values associated with spatial data can be used to constrain spatial operations — for instance, spatial operations cannot be performed between spatial objects with differing SRIDs in some systems, or trigger coordinate system transformations between spatial objects in others. ## See also - [Engineering datum](/source/Engineering_datum) - [Geodesy](/source/Geodesy) - [Geodetic datum](/source/Geodetic_datum) - [Georeferencing](/source/Georeferencing) - [Geographic coordinate systems](/source/Geographic_coordinate_systems) - [Geographic information system](/source/Geographic_information_system) ([GIS](/source/Geographic_information_system)). - [Grid reference](/source/Grid_reference) - [Linear referencing](/source/Linear_referencing) - [List of National Coordinate Reference Systems](/source/List_of_National_Coordinate_Reference_Systems) - [Terms of orientation](/source/Terms_of_orientation) ## References 1. ^ [***a***](#cite_ref-epsg_1-0) [***b***](#cite_ref-epsg_1-1) ["Using the EPSG geodetic parameter dataset, Guidance Note 7-1"](https://epsg.org/guidance-notes.html). *EPSG Geodetic Parameter Dataset*. Geomatic Solutions. [Archived](https://web.archive.org/web/20211215215824/https://epsg.org/guidance-notes.html) from the original on 15 December 2021. Retrieved 15 December 2021. 1. ^ [***a***](#cite_ref-ogc_as_2-0) [***b***](#cite_ref-ogc_as_2-1) ["OGC Abstract Specification Topic 2: Referencing by coordinates Corrigendum"](https://docs.ogc.org/as/18-005r5/18-005r5.html). *Open Geospatial Consortium*. [Archived](https://web.archive.org/web/20210730043924/http://docs.ogc.org/as/18-005r5/18-005r5.html) from the original on 2021-07-30. Retrieved 2018-12-25. 1. **[^](#cite_ref-OSGB_3-0)** [*A guide to coordinate systems in Great Britain*](https://web.archive.org/web/20150924061607/http://www.ordnancesurvey.co.uk/docs/support/guide-coordinate-systems-great-britain.pdf) (PDF), D00659 v2.3, Ordnance Survey, 2020, p. 11, archived from [the original](https://www.ordnancesurvey.co.uk/documents/resources/guide-coordinate-systems-great-britain.pdf) (PDF) on 24 September 2015, retrieved 2021-12-16 ## External links [Wikidata](/source/Wikidata) has the property: - ***[spatial reference system (P3037)](https://www.wikidata.org/wiki/Property_talk:P3037)*** (see [uses](https://query.wikidata.org/embed.html#SELECT%20%3FWikidata_item_%20%3FWikidata_item_Label%20%3Fvalue%20%3FvalueLabel%20%3FEnglish_Wikipedia_article%20%23Show%20data%20in%20this%20order%0A%7B%0A%09%3FWikidata_item_%20wdt%3AP3037%20%3Fvalue%20.%20%23Collecting%20all%20items%20which%20have%20P3037%20data%2C%20from%20whole%20Wikidata%20item%20pages%0A%09OPTIONAL%20%7B%3FEnglish_Wikipedia_article%20schema%3Aabout%20%3FWikidata_item_%3B%20schema%3AisPartOf%20%3Chttps%3A%2F%2Fen.wikipedia.org%2F%3E%20.%7D%20%23If%20collected%20item%20has%20link%20to%20English%20Wikipedia%2C%20show%20that%0A%09SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22en%22%20%20%7D%20%23Show%20label%20in%20this%20language.%20%22en%22%20is%20English.%20%20%20%0A%7D%0ALIMIT%201000)) - [spatialreference.org](https://spatialreference.org/) – A website with more than 13000 spatial reference systems, in a variety of formats. - [OpenGIS Specifications (Standards)](http://www.opengeospatial.org/specs/?page=specs) [Archived](https://web.archive.org/web/20041213090611/http://www.opengeospatial.org/specs/?page=specs) 2004-12-13 at the [Wayback Machine](/source/Wayback_Machine) - [OpenGIS Simple Features Specification for CORBA (99-054)](http://www.opengeospatial.org/standards/sfc) - [OpenGIS Simple Features Specification for OLE/COM (99-050)](http://www.opengeospatial.org/standards/sfo) - [OpenGIS Simple Features Specification for SQL (99-054, 05-134, 06-104r3)](http://www.opengeospatial.org/standards/sfs) - [OGR](http://www.gdal.org/ogr/) [Archived](https://web.archive.org/web/20060422001312/http://www.gdal.org/ogr/) 2006-04-22 at the [Wayback Machine](/source/Wayback_Machine) — library implementing relevant OGC standards - [EPSG.org](https://epsg.org/) - Official EPSG Geodetic Parameter Dataset webpage. Search engine for EPSG defined reference systems. - [EPSG.io/](http://www.epsg.io/) - Full text search indexing over 6000 coordinate systems - [Galdos Systems INdicio CRS Registry](http://www.galdosinc.com/products/indicio-crs-registry) v t e Standards of the Open Geospatial Consortium (OGC) CSW GeoPackage GeoRSS GeoSPARQL GML KML O&M OGC Reference Model SensorML SOS SFA SLD SRID TransducerML TMS WaterML WCS WFS WMS WMTS WPS v t e International Organization for Standardization (ISO) standards List of ISO standards – ISO romanizations – IEC standards 1–9999 1 2 3 4 6 7 9 16 17 31 -0 -1 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 68-1 128 216 217 226 228 233 259 261 262 302 306 361 500 518 519 639 -1 -2 -3 -5 -6 646 657 668 690 704 732 764 838 843 860 898 965 999 1000 1004 1007 1073-1 1073-2 1155 1413 1538 1629 1745 1989 2014 2015 2022 2033 2047 2108 2145 2146 2240 2281 2533 2709 2711 2720 2788 2848 2852 2921 3029 3103 3166 -1 -2 -3 3297 3307 3601 3602 3864 3901 3950 3977 4031 4157 4165 4217 4909 5218 5426 5427 5428 5725 5775 5776 5800 5807 5964 6166 6344 6346 6373 6385 6425 6429 6438 6523 6709 6943 7001 7002 7010 7027 7064 7098 7185 7200 7498 -1 7637 7736 7810 7811 7812 7813 7816 7942 8000 8093 8178 8217 8373 8501-1 8571 8583 8601 8613 8632 8651 8652 8691 8805/8806 8807 8820-5 8859 -1 -2 -3 -4 -5 -6 -7 -8 -8-I -9 -10 -11 -12 -13 -14 -15 -16 8879 9000/9001 9036 9075 9126 9141 9227 9241 9293 9314 9362 9407 9496 9506 9529 9564 9592/9593 9594 9660 9797-1 9897 9899 9945 9984 9985 9995 10000–19999 10006 10007 10116 10118-3 10160 10161 10165 10179 10206 10218 10279 10303 -11 -21 -22 -28 -238 10383 10585 10589 10628 10646 10664 10746 10861 10957 10962 10967 11073 11170 11172 11179 11404 11544 11783 11784 11785 11801 11889 11898 11940 (-2) 11941 11941 (TR) 11992 12006 12052 12182 12207 12234-2 12620 13211 -1 -2 13216 13250 13399 13406-2 13450 13485 13490 13567 13568 13584 13616 13816 13818 14000 14031 14224 14289 14396 14443 14496 -2 -3 -6 -10 -11 -12 -14 -17 -20 14617 14644 14649 14651 14698 14764 14882 14971 15022 15118 15189 15288 15291 15398 15408 15444 -3 -9 15445 15438 15504 15511 15686 15693 15706 -2 15707 15897 15919 15924 15926 15926 WIP 15930 15938 16023 16262 16355-1 16485 16612-2 16750 16949 (TS) 17024 17025 17100 17203 17369 17442 17506 17799 18004 18014 18181 18245 18629 18760 18916 19005 19011 19092 -1 -2 19114 19115 19125 19136 19407 19439 19500 19501 19502 19503 19505 19506 19507 19508 19509 19510 19600 19650 19752 19757 19770 19775-1 19794-5 19831 20000–29999 20000 20022 20121 20400 20802 20830 21000 21001 21047 21122 21500 21778 21827 22000 22275 22300 22301 22395 22537 23000 23003 23008 23009 23090-3 23092 23094-1 23094-2 23270 23271 23360 23941 24517 24613 24617 24707 24728 25178 25964 26000 26262 26300 26324 27000 series 27000 27001 27002 27005 27006 27729 28000 29110 29148 29199-2 29500 30000+ 30170 31000 32000 37001 38500 39075 40230 40240 40250 40260 40314 40500 42010 45001 50001 55000 56000 80000 Category --- Adapted from the Wikipedia article [Spatial reference system](https://en.wikipedia.org/wiki/Spatial_reference_system) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Spatial_reference_system?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.