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In surveying, an initial point is a
A principal meridian and base line are usually established based on a preselected initial point, often some distinct geographical feature. As an example, the first established initial point in California was the Mount Diablo meridian. It was chosen because the summit of
In surveying, an initial point is a datum
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted. ...
(a specific point on the surface of the earth) that marks the beginning point for a cadastral survey
Cadastral surveying is the sub-field of cadastre and surveying that specialises in the establishment and re-establishment of real property boundaries. It involves the physical delineation of property boundaries and determination of dimensions, a ...
. The initial point establishes a local geographic coordinate system for the surveys that refer to that point.
An initial point is defined by the intersection of a principal meridian
A principal meridian is a meridian 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 Greenwich, just west of Wi ...
and a base line.
Selection of initial points
A principal meridian and base line are usually established based on a preselected initial point, often some distinct geographical feature. As an example, the first established initial point in California was the Mount Diablo meridian. It was chosen because the summit of Mount Diablo
Mount Diablo is a mountain of the Diablo Range, in Contra Costa County of the eastern San Francisco Bay Area in Northern California. It is south of Clayton and northeast of Danville. It is an isolated upthrust peak of , visible from most ...
could be seen for many miles around and could be referenced for surveys.
In other cases, a meridian and a base line were chosen separately based on other geographical features. For example, the Fifth principal meridian in the new Louisiana Purchase
The Louisiana Purchase (french: Vente de la Louisiane, translation=Sale of Louisiana) was the acquisition of the territory of Louisiana by the United States from the French First Republic in 1803. In return for fifteen million dollars, or app ...
was established in 1815, with its southern end based on the confluence of the Arkansas
Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the O ...
and Mississippi
Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Miss ...
Rivers, and extended northward from that point. The eastern end of the base line was chosen as the confluence of the St. Francis and Mississippi Rivers and extended westward. The initial point would be established where the meridian and the base line crossed, which turned out to be in the middle of a swamp in eastern Arkansas
Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the O ...
. This point is now located in the Louisiana Purchase State Park
The Louisiana Purchase Historic State Park, located in eastern Arkansas, commemorates the initial point from which the lands acquired through the Louisiana Purchase were subsequently surveyed. The park encompasses of forested wetlands, a landf ...
.
Some initial points were chosen based on existing markers. The initial point for the Gila and Salt River meridian was established based on an existing marker that had been set up in 1851 to mark a point on the Mexico–United States border
The Mexico–United States border ( es, frontera Estados Unidos–México) is an international border separating Mexico and the United States, extending from the Pacific Ocean in the west to the Gulf of Mexico in the east. The border trave ...
before the Gadsden Purchase.
Many of the initial points in the United States have been listed on the National Register of Historic Places
The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic ...
.
Notable initial points include:
* Beginning Point of the U.S. Public Land Survey
* Initial Point (Oklahoma)
* Initial Point of Boundary Between U.S. and Mexico, California
* Initial Point of the Gila and Salt River Base Line and Meridian, Arizona
* Mason and Dixon Survey Terminal Point, West Virginia
See also
*Public Land Survey System
The Public Land Survey System (PLSS) is the surveying method developed and used in the United States to plat, or divide, real property for sale and settling. Also known as the Rectangular Survey System, it was created by the Land Ordinance of 178 ...
*List of principal and guide meridians and base lines of the United States
This is a list of principal and guide meridians and base lines of the United States, with the year established and a brief summary of what areas' land surveys are based on each.
List of meridians
Primarily from the United States Government Pr ...
*References
External links
* *{{cite web , url =http://www.blm.gov/wo/st/en/prog/more/cadastralsurvey.html , title =Cadastral Survey , publisher =U.S. Bureau of Land Management , accessdate =2012-10-09 , archive-url =https://web.archive.org/web/20121006201652/http://www.blm.gov/wo/st/en/prog/more/cadastralsurvey.html , archive-date =2012-10-06 , url-status =dead *