Vol. 1, No. 1, 2013

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Ptolemy's longitudes and Eratosthenes' measurement of the earth's circumference

Lucio Russo

Vol. 1 (2013), No. 1, 67–79

A statistical analysis of the longitudes reported in Ptolemy’s Geographia shows that many of them were obtained by distorting in a linear way data which were known with good accuracy. As a consequence, a new estimate of the value of the stadion used by Eratosthenes is obtained, supporting the thesis that his measurement of the Earth’s circumference was remarkably accurate. Some conjectures about possible simplifications introduced by Cleomedes in his account of Eratosthenes’ method are also proposed.

Eratosthenes' measurement, Ptolemy's geography, stadion
Mathematical Subject Classification 2010
Primary: 01A20
Received: 21 September 2012
Revised: 31 October 2012
Accepted: 2 December 2012
Published: 6 February 2013

Communicated by Raffaele Esposito
Lucio Russo
Department of Mathematics
Università di Roma Tor Vergata
via Keplero 10
I-00142 Roma