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Jul 12, 2018 · What are NAD 27 and NAD 83? The North American Datum of 1927 (NAD 27) is "The horizontal control datum for the United States that (was) defined by (a) location and azimuth on the Clarke spheroid of 1866, with origin at (the survey station) Meades Ranch." ...
NADCON is the Federal standard for NAD 27 to NAD 83 datum transformations. NADCON Documentation. Download the NADCON program and Data Grids for PC execution. Interactively compute a datum shift between NAD 27 and NAD 83. Interactively compute a datum shift between NAD 83 and a HPGN.
The NAD 27 is a horizontal datum for the continental United States based on the Clarke ellipsoid of 1866 (Clarke 1866). The fixed datum reference point is located at Meades Ranch, Kansas.The longitude origin of NAD 27 is the Greenwich Meridian with a south azimuth orientation.
Within the conterminous 48 states, the North American Datum of 1927 (NAD 27) to the North American Datum of 1983 (NAD 83) shift of the latitude/longitude graticule (lines showing parallels of latitude and meridians of longitude for the earth) is in the range of 10-100 ground meters.
The North American Datum of 1927 (NAD 27) and the National Geodetic Vertical Datum of 1929 (NGVD 29) are considered superseded as the national standards.
Mar 10, 2024 · A horizontal datum (like NAD27) is a model that translates an ellipsoid into latitude and longitude coordinates. NAD27 put a fixed latitude and longitude position at Meade’s Ranch, Kansas (39° 13’26.686″ north latitude, 98° 32’30.506″ west longitude). This was because it was near the center of the contiguous United States.
It is the reference ellipsoid of the datum known as the North American Datum of 1927 (NAD27), but it is not the datum itself. For the Clarke 1866 spheroid to become NAD27, the ellipsoid of reference had to be attached at a point and specifically oriented to the actual surface of the earth.
