North American Datum - North American Datum of 1983

North American Datum of 1983

Because Earth deviates significantly from a perfect ellipsoid, the ellipsoid that best approximates its shape varies region by region across the world. Clarke 1866, and North American Datum of 1927 with it, were surveyed to best suit North America as a whole. Likewise, historically most regions of the world used ellipsoids measured locally to best suit the vagaries of earth's shape in their respective locales. While ensuring the most accuracy locally, this practice makes integrating and disseminating information across regions troublesome.

As satellite geodesy and remote sensing technology reached high precision and were made available for civilian applications, it became feasible to acquire information referred to a single global ellipsoid. This is because satellites naturally deal with Earth as a monolithic body. Therefore the GRS 80 ellipsoid was developed for best approximating the earth as a whole, and it became the foundation for the North American Datum of 1983. Though generally GRS 80 and its close relative WGS 84 are not the best fit for any given region, a need for the closest fit largely evaporates when a global survey is combined with computers, databases, and software able to compensate for local conditions.

Ellipsoid Semimajor axis† Semiminor axis†† Inverse flattening††
GRS 80 6,378,137 m 6,356,752.3141 m 298.257222101

†By definition. ††Calculated.

Read more about this topic:  North American Datum

Famous quotes containing the words north, american and/or datum:

    We have heard all of our lives how, after the Civil War was over, the South went back to straighten itself out and make a living again. It was for many years a voiceless part of the government. The balance of power moved away from it—to the north and the east. The problems of the north and the east became the big problem of the country and nobody paid much attention to the economic unbalance the South had left as its only choice.
    Lyndon Baines Johnson (1908–1973)

    All great religions, in order to escape absurdity, have to admit a dilution of agnosticism. It is only the savage, whether of the African bush or the American gospel tent, who pretends to know the will and intent of God exactly and completely.
    —H.L. (Henry Lewis)

    Language fails not because thought fails, but because no verbal symbols can do justice to the fullness and richness of thought. If we are to continue talking about “data” in any other sense than as reflective distinctions, the original datum is always such a qualitative whole.
    John Dewey (1859–1952)