North American Datum of 1927
The North American Datum of 1927 (NAD27) is based on the Clarke Ellipsoid of 1866; it was created by manual surveying of the entire continent. The geodetic "center" of NAD27 is a base station at Meades Ranch in Kansas.
| Ellipsoid | Semimajor axis† | Semiminor axis† | Inverse flattening†† |
| Clarke 1866 | 6,378,206.4 m | 6,356,583.8 m | 294.978698214 |
†By definition. ††Calculated.
These are the defining dimensions for NAD27, but Clarke actually defined his 1866 spheroid as a = 20,926,062 British feet, b = 20,855,121 British feet. The conversion to meters uses Clarke's 1865 inch-meter ratio of 39.370432. In a practical sense, the length of a foot or meter at the time could not be benchmarked to better than about 0.02 mm, so the meter equivalents used now can be considered exact to well beyond the uncertainties in the lengths and conversion values of the time.
Read more about this topic: North American Datum
Famous quotes containing the words north american, north, american and/or datum:
“The compulsion to do good is an innate American trait. Only North Americans seem to believe that they always should, may, and actually can choose somebody with whom to share their blessings. Ultimately this attitude leads to bombing people into the acceptance of gifts.”
—Ivan Illich (b. 1926)
“Come see the north wind’s masonry.
Out of an unseen quarry evermore
Furnished with tile, the fierce artificer
Curves his white bastions with projected roof”
—Ralph Waldo Emerson (1803–1882)
“I believe no satirist could breathe this air. If another Juvenal or Swift could rise up among us tomorrow, he would be hunted down. If you have any knowledge of our literature, and can give me the name of any man, American born and bred, who has anatomised our follies as a people, and not as this or that party; and who has escaped the foulest and most brutal slander, the most inveterate hatred and intolerant pursuit; it will be a strange name in my ears, believe me.”
—Charles Dickens (1812–1870)
“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)