Editing Geographic coordinate system (section)

{{Short description|System to specify locations on Earth}}
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{{Broader|Spatial reference system}}
{{Use dmy dates|date=May 2019}}
{{Use American English|date=June 2024}}
[[File:FedStats Lat long.svg|thumb|upright=1.2|Longitude lines are perpendicular to and latitude lines are parallel to the Equator.]]
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A '''geographic coordinate system''' ('''GCS''') is a [[spherical coordinate system|spherical]] or [[geodetic coordinates|geodetic coordinate]] system for measuring and communicating [[position (geometry)|positions]] directly on [[Earth]] as [[latitude]] and [[longitude]].<ref name="chang2016">{{cite book |last1=Chang |first1=Kang-tsung |title=Introduction to Geographic Information Systems |date=2016 |publisher=McGraw-Hill |isbn=978-1-259-92964-9 |page=24 |edition=9th}}</ref> It is the simplest, oldest, and most widely used type of the various [[spatial reference systems]] that are in use, and forms the basis for most others. Although latitude and longitude form a coordinate [[tuple]] like a [[cartesian coordinate system]], the geographic coordinate system is not cartesian because the measurements are angles and are not on a planar surface.<ref name="DiBiase">{{cite web |last=DiBiase |first=David |title=The Nature of Geographic Information |url=https://www.e-education.psu.edu/natureofgeoinfo/c2_p10.html |access-date=18 February 2024 |archive-date=19 February 2024 |archive-url=https://web.archive.org/web/20240219075125/https://www.e-education.psu.edu/natureofgeoinfo/c2_p10.html |url-status=live }}</ref>

A full GCS specification, such as those listed in the [[EPSG Geodetic Parameter Dataset|EPSG]] and ISO 19111 standards, also includes a choice of [[geodetic datum]] (including an [[Earth ellipsoid]]), as different datums will yield different latitude and longitude values for the same location.<ref name="epsg">{{cite web |title=Using the EPSG geodetic parameter dataset, Guidance Note 7-1 |url=https://epsg.org/guidance-notes.html |website=EPSG Geodetic Parameter Dataset |publisher=Geomatic Solutions |access-date=15 December 2021 |archive-date=15 December 2021 |archive-url=https://web.archive.org/web/20211215215824/https://epsg.org/guidance-notes.html |url-status=live }}</ref>