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.
Keywords
Eratosthenes' measurement, Ptolemy's geography, stadion
