surveying Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ...

, an initial point is a datum (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, area ...

. The initial point establishes a local

geographic coordinate system The geographic coordinate system (GCS) is a spherical or ellipsoidal coordinate system for measuring and communicating positions directly on the Earth as latitude and longitude. It is the simplest, oldest and most widely used of the vari ...

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

Systemic numbering in the Public Land Survey System

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 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 In geography, a confluence (also: ''conflux'') occurs where two or more flowing bodies of water join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river ( main stem); ...

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 ...

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. Mis ...

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

. This point is now located in the Louisiana Purchase State Park. 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 trav ...

before the

Gadsden Purchase The Gadsden Purchase ( es, region=MX, la Venta de La Mesilla "The Sale of La Mesilla") is a region of present-day southern Arizona and southwestern New Mexico that the United States acquired from Mexico by the Treaty of Mesilla, which took effe ...

. 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 artist ...

. Notable initial points include: *

Beginning Point of the U.S. Public Land Survey The Beginning Point of the U.S. Public Land Survey is the point from which the United States in 1786 began the formal survey of the lands known then as the Northwest Territory, now making up all or part of Ohio, Indiana, Illinois, Michigan, and Wis ...

* Initial Point (Oklahoma) *

Initial Point of Boundary Between U.S. and Mexico The Initial Point of Boundary Between U.S. and Mexico (Monument No. 258) is the westernmost boundary marker on the international boundary between the United States and Mexico and as such has since its erection marked the southwestern corner of th ...

, California * Initial Point of the Gila and Salt River Base Line and Meridian, Arizona * Mason and Dixon Survey Terminal Point, West Virginia

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 *

Selection of initial points

See also

References

External links