Principal meridian
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[[Image:Meridians-baselines.png|thumb|500px|right|Figure 1. This BLM map depicts the principal meridians and [[baseline (surveying)|baselines]] used for surveying states (colored) in the PLSS.]]
A [[meridian (geography)|meridian]] is an imaginary line on the Earth's surface from the [[North Pole]] to the [[South Pole]] that connects all locations with a given [[longitude]]. Each is half of a [[great circle]] on the Earth's surface. A '''principal meridian''' is the principal north-south line used for survey control in a large region.
==Canada==
The [[Dominion Land Survey]] of [[Western Canada]] took its origin at the First (or Principal) Meridian, located at 97°27′28.41″ west of [[Prime Meridian|Greenwich]], just west of [[Winnipeg, Manitoba]].
Six other meridians were designated at four-degree intervals westward, with the seventh located in British Columbia; the second and fourth meridians form the general eastern border and the western border of [[Saskatchewan]].
==United States==
In the [[United States]] [[Public Land Survey System]], a '''principal meridian''' is the principal north-south line used for survey control in a large region, and which divides townships between east and west. The meridian meets its corresponding [[baseline (surveying)|baseline]] at the point of origin, or '''initial point''', for the land survey. For example, the [[Mount Diablo Meridian]], used for surveys in California and Nevada, runs through the summit of [[Mount Diablo State Park|Mount Diablo]].
Often, meridians are marked with roads, such as the Meridian Avenue in [[San Jose, California]], Meridian Road in [[Vacaville, California]], both on the [[Mount Diablo Meridian]], Meridian Road in [[Wichita, Kansas]] on the Sixth Principal Meridian, and Meridian Avenue in several western Washington counties generally following the Willamette Meridian. Baseline Rd or Base Line St. extends for about 60 miles from Highland, CA (east of San Bernardino) to the Pacific Coast in Santa Monica, CA.
== See also ==
* [[Cardo]]
* [[Baseline (surveying)]]
==External links==
*[http://www.pmproject.org/ The Principal Meridian Project (US)]
[[Category:Surveying]]
[[Category:Lines of longitude]]
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