Editing Geographic coordinate system (section)

== History ==
{{see also|History of geodesy}}

The [[invention]] of a geographic coordinate system is generally credited to [[Eratosthenes]] of [[Cyrene, Libya|Cyrene]], who composed his now-lost ''[[Geography (Eratosthenes)|Geography]]'' at the [[Library of Alexandria]] in the 3rd century&nbsp;BC.<ref>{{Citation |last=McPhail |first=Cameron |title=Reconstructing Eratosthenes'<!--sic--> Map of the World |pages=20–24 |url=https://ourarchive.otago.ac.nz/bitstream/handle/10523/1713/McPhailCameron2011MA.pdf |year=2011 |publisher=University of Otago |location=[[Dunedin]] |access-date=14 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402095830/https://ourarchive.otago.ac.nz/bitstream/handle/10523/1713/McPhailCameron2011MA.pdf |url-status=live }}.</ref> A century later, [[Hipparchus#Geography|Hipparchus]] of [[Nicaea]] improved on this system by determining latitude from stellar measurements rather than solar altitude and determining longitude by timings of [[lunar eclipse]]s, rather than [[dead reckoning]]. In the 1st or 2nd century, [[Marinus of Tyre]] compiled an extensive gazetteer and [[equirectangular projection|mathematically plotted world map]] using coordinates measured east from a [[prime meridian]] at the westernmost known land, designated the [[Fortunate Isles]], off the coast of western Africa around the [[Canary Islands|Canary]] or [[Cape Verde|Cape Verde Islands]], and measured north or south of the island of [[Rhodes]] off [[Asia Minor]]. [[Ptolemy]] credited him with the full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the [[midsummer]] day.<ref>{{Citation |last=Evans |first=James |title=The History and Practice of Ancient Astronomy |url=https://books.google.com/books?id=LVp_gkwyvC8C&pg=PA102 |pages=102–103 |publisher=Oxford University Press |year=1998 |location=Oxford, England |isbn=9780199874453 |access-date=5 May 2020 |archive-date=17 March 2023 |archive-url=https://web.archive.org/web/20230317171201/https://books.google.com/books?id=LVp_gkwyvC8C&pg=PA102 |url-status=live }}.</ref>

Ptolemy's 2nd-century ''[[Geography (Ptolemy)|Geography]]'' used the same prime meridian but measured latitude from the [[Equator]] instead. After their work was translated into [[Arabic]] in the 9th century, [[Al-Khwarizmi|Al-Khwārizmī]]'s ''[[Book of the Description of the Earth]]'' corrected Marinus' and Ptolemy's errors regarding the length of the [[Mediterranean Sea]],{{NoteTag|The pair had accurate absolute distances within the Mediterranean but underestimated the [[circumference of the Earth]], causing their degree measurements to overstate its length west from Rhodes or Alexandria, respectively.}} causing [[Geography and cartography in the medieval Islamic world|medieval Arabic cartography]] to use a prime meridian around 10° east of Ptolemy's line. Mathematical cartography resumed in Europe following [[Maximus Planudes]]' recovery of Ptolemy's text a little before 1300; the text was translated into [[Latin]] at [[Republic of Florence|Florence]] by [[Jacopo d'Angelo]] around 1407.<!--more sources at linked pages-->

In 1884, the [[United States]] hosted the [[International Meridian Conference]], attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the [[Royal Observatory, Greenwich|Royal Observatory]] in [[Greenwich]], England as the zero-reference line. The [[Dominican Republic]] voted against the motion, while France and [[Brazil]] abstained.<ref>{{cite web |publisher=Greenwich 2000 Limited |url = http://wwp.millennium-dome.com/info/conference.htm |title=The International Meridian Conference |website=Millennium Dome: The O2 in Greenwich |date=9 June 2011 |access-date=31 October 2012 |url-status=dead |archive-url = https://web.archive.org/web/20120806065207/http://wwp.millennium-dome.com/info/conference.htm |archive-date=6 August 2012 }}</ref> France adopted [[Greenwich Mean Time]] in place of local determinations by the [[Paris Observatory]] in 1911.