The North American Datum is the official datum used for the primary geodetic network in North America. This article describes a concept from Surveying and Geodesy. For other meanings see Datum (disambiguation. Geodesy (dʒiːˈɒdɪsi also called geodetics, a branch of Earth sciences, is the scientific discipline that deals In the fields of cartography and land-use there are currently two North American Datums in use: the North American Datum of 1927 (NAD 27) and the North American Datum of 1983 (NAD 83). Both are geodetic reference systems, but each is based on different measurements.
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North American Datum of 1927
The North American Datum of 1927 (NAD27) is a datum based on the Clarke Ellipsoid of 1866. Alexander Ross Clarke (1828-1914 was a British geodesist primarily remembered for his work defining different Reference ellipsoids approximating the shape of the Geoid In Geodesy, a reference ellipsoid is a mathematically-defined surface that approximates the Geoid, the truer Figure of the Earth, or other planetary body This Ellipsoid was created by way of manual surveying of the entire continent. The geodetic "center" of NAD-27 is a base station at Meades Ranch in Kansas. Meades Ranch in Kansas is designated as the geodetic base point for the North American Datum of 1927 ( NAD 27) at (39
North American Datum of 1983
As satellite and remote sensing technology both improved and were made available for civilian applications, it became obvious that the NAD-27's appromixations were not sufficiently accurate. This article is about artificial satellites For natural satellites also known as moons see Natural satellite. Remote sensing is the small or large-scale acquisition of information of an object or phenomenon by the use of either recording or real-time sensing device(s that is not in physical A civilian under International humanitarian law is a person who is not a member of his or her Country 's Armed forces.
The North American Datum of 1983 was created to meet requirements for better accuracy and more precision. It is based on the GRS80 ellipsoid; an ellipsoid derived from satellite geodesy. GRS 80, or Geodetic Reference System 1980, is a Geodetic reference system consisting of a global Reference ellipsoid and a Gravity field model This article is about artificial satellites For natural satellites also known as moons see Natural satellite. Geodesy (dʒiːˈɒdɪsi also called geodetics, a branch of Earth sciences, is the scientific discipline that deals
| Ellipsoid | Semi-major axis | Eccentricity Squared |
| NAD 83 | 6,378,137 m | 0. 006694300229 |
Comparisons Between NAD-27 and NAD-83
A point having a given latitude and longitude in NAD27 may be displaced on the order of many tens of meters from another point having the identical latitude and longitude in NAD83. So it is important to specify the datum along with the coordinates. The North American Datum of 1927 is defined by the latitude and longitude of an initial point (Meades Ranch in Kansas), the direction of a line between this point and a specified second point, and two dimensions that define the spheroid. Meades Ranch in Kansas is designated as the geodetic base point for the North American Datum of 1927 ( NAD 27) at (39 Equation A spheroid centered at the origin and rotated about the z axis is defined by the implicit equation \left(\frac{x}{a}\right^2+\left(\frac{y}{a}\right^2+\left(\frac{z}{b}\right^2 The North American Datum of 1983 is based on a newer defined spheroid (GRS80); it is an Earth-centered datum having no initial point or initial direction.
External links
- NADCON – a free utility to convert between NAD27 and NAD83
- nadcon.prl – a web-based utility for NADCON
- NAD27/NAD83 Conversion Tool - free online conversion between NAD27 and NAD83 datums
See also
The World Geodetic System defines a reference frame for the earth for use in Geodesy and Navigation.Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic