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, north, american and/or datum:
“The North American system only wants to consider the positive aspects of reality. Men and women are subjected from childhood to an inexorable process of adaptation; certain principles, contained in brief formulas are endlessly repeated by the press, the radio, the churches, and the schools, and by those kindly, sinister beings, the North American mothers and wives. A person imprisoned by these schemes is like a plant in a flowerpot too small for it: he cannot grow or mature.”
—Octavio Paz (b. 1914)
“I meet him at every turn. He is more alive than ever he was. He has earned immortality. He is not confined to North Elba nor to Kansas. He is no longer working in secret. He works in public, and in the clearest light that shines on this land.”
—Henry David Thoreau (1817–1862)
“Even an attorney of moderate talent can postpone doomsday year after year, for the system of appeals that pervades American jurisprudence amounts to a legalistic wheel of fortune, a game of chance, somewhat fixed in the favor of the criminal, that the participants play interminably.”
—Truman Capote (1924–1984)
“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)