page_title: Meades Ranch Triangulation Station
section_title: Meades Ranch station
hierarchical_section_title: Meades Ranch Triangulation Station / History / Meades Ranch station
caption_attribution_description: Horizontal Control Network of the United States June 1931
context_page_description: The Meades Ranch Triangulation Station is a survey marker in Osborne County in the state of Kansas in the Midwestern United States. The marker was initially placed in 1891; from 1901 to 1989, it was the reference location relative to which all locations in the United States were measured, and from 1913 to 1989, it was the reference location for all surveys in the continent.
  In 1973, the site was listed in the National Register of Historic Places as Geodetic Center of the United States.
context_section_description: The U.S. Coast and Geodetic Survey established a triangulation station, officially known as the Meades Ranch Triangulation Station, in 1891.  The location lay near the intersection of two transcontinental arcs of triangulation: one running from the Atlantic to the Pacific Ocean, roughly following the 39th parallel; the other running from Mexico to Canada, along the 98th meridian.
  In 1901, the Meades Ranch station was chosen as the United States standard horizontal datum: the point relative to which all land measurements in the nation were made.  The choice was based on the station's location near the geographic center of the U.S. and near the intersection of the two arcs of triangulation, and because it minimized the number of changes in previously published positions.  Its position was officially set as 39°13'26.686" N and 98°32'30.506" W; the azimuth direction to a triangulation station near Waldo, southwest of Meades Ranch, was officially set as 75°28'14.52" west of south.
  In 1913, the chief astronomer of the Dominion of Canada Astronomical Observatory and the director of the Comisión Geodésica Mexicana announced that their organizations would use the Meades Ranch location as their standard datum.  In light of this, its name was changed to the "North American Datum".
  As more new surveys and previously isolated survey networks were incorporated into the system, it became increasingly difficult to make the necessary corrections.  By the mid-1920s, it was realized that the coordinate system needed to be adjusted.  From 1927 to 1932, the approximately 25,000 existing control locations were recalculated and a new coordinate system developed, known as NAD27.  The new system continued to use the 1901 coordinates of Meades Ranch as its horizontal datum, and the Clarke spheroid as its model for the Earth's surface.  However, it now defined horizontal directions in terms of 175 Laplace azimuths, which use astronomical azimuths corrected for the difference between the astronomic and geodetic meridians.  Under NAD27, the azimuth to the Waldo station changed by about 5".
  In 1973, the Meades Ranch site was added to the National Register of Historic Places, under the name "Geodetic Center of the United States".
caption: Horizontal survey control network in the United States in 1931
exif: {}