Who first estimated the circumfirance of the earth and how close to the actual measurement was he?

Question

Answer first correctly gets best answer

Answer 1

Eratosthenes -- within 2%

Answer 2

Ancient Measurements of the Circumference of the Earth
http://www.metrum.org/measures/measurements.htm

"[...] This very fact proves that Eratosthenes did not proceed to any actual measurement. Some of the French scholars had doubted that Eratosthenes had proceeded to an actual measurement of the degree. Letronne concluded that Eratosthenes calculated the latitude of Alexandria and the latitude of Syene and then calculated the length of the degree.

In my opinion Eratosthenes did try to apply to Egypt the figure about the length of the degree current in the Greek world, that of 20 parasangs or 75 Roman miles to the degree; but he proceeded in a manner different from that suggested by Letronne. [...]

There is a score of articles trying to prove in detail that Eratosthenes proceeded to an independent evaluation of the circumference of the earth; but even though some of them show great ingenuity, none succeeds. The result ascribed to Eratosthenes, that is, a circumference of 250,000 stadia, repeats the traditional datum. [...]"

http://en.wikipedia.org/wiki/Eratosthenes

"Eratosthenes knew that on the summer solstice at local noon in the town of Syene on the Tropic of Cancer, the sun would appear at the zenith, directly overhead. He also knew, from measurement, that in his hometown of Alexandria, the angle of elevation of the Sun would be 7.2° south of the zenith at the same time. Assuming that Alexandria was due north of Syene he concluded that the distance from Alexandria to Syene must be 7.2/360 of the total circumference of the Earth. The distance between the cities was known from caravan travellings to be about 5000 stadia: approximately 800 km. He established a final value of 700 stadia per degree, which implies a circumference of 252,000 stadia. The exact size of the stadion he used is no longer known (the common Attic stadion was about 185 m), but it is generally believed that the circumference calculated by Eratosthenes corresponds to 39,690 km [citation needed]. The estimate is over 99% of the actual distance of 40,008 km."

Answer 3

Eratosthenes measured it, and is generally credited as being within 1%. However, we can't be certain how accurate he was as he measured it in stadia, and we can't be sure how long a stadium was. Two of the basic assumptions he made in his calculation - namely that Syene is on the tropic of Cancer and that Alexandria is due north of it, are both wrong, so I'm doubtful that he was that close..

Answer 4

The geometry of the earth was known before the Greeks . However it was a greek that calculated the cirumference of the earth by calulating the lenght of shadow per degree.and over 360 degree obtained the circumference and diametre of the earth.
HIs name was Erastothenes. The error of his measurement was for practical purpose neglible.

Answer 5

Dang, Jon gets the points. (Though I heard it was closer to three percent error.)