''I have analyzed all other ancient authors who provide information about the dimensions of the Pyramid. By a careful collation of their words and phrases, I have established that they all draw, directly or indirectly, on a single source. These authors wrote in Greek or in Latin during the first century of the Roman Empire. They are the historian Diodorus of Sicily (1, 63), the geographer Strabo (XVII, 1, 33), the encyclopedist Pliny the Elder (XXVI, 12, 78-80), and the engineer Philon of Byzantium (Wonders of the World, II). Their common source is the Greek grammarian Agatharchides of Cnidus, who toward the end of the second century B.C. was the guardian to one of the Ptolemy kings of Egypt. Quotations from Agatharchides’ lost works indicate that he wrote extensively on the geography of Egypt, with particular emphasis on natural science. . .
From the authors who drew on Agatharchides we gather that he said that the perimeter [of the Great Pyramid] is 5 stadia, that is, 1/2 minute of degree. . .
One would have expected the perimeter of the Pyramid to have been calculated by the length of the degree of longitude at the equator, but the builders instead calculated by the degree of latitude. . .
Agatharchides wanted also to emphasize that the dimensions of the Pyramid were related to the length of the degree of latitude.
The basic idea of the Great Pyramid was that it should be a representation of the northern hemisphere, a hemisphere projected on flat surfaces, as is done in mapmaking. . .
The Great Pyramid was a projection on four triangular surfaces. The apex represented the pole and the perimeter represented the equator. This is the reason why the perimeter is in relation 2 pi with the height.
The Great Pyramid represents the northern hemisphere in a scale 1:43,200; this scale was chosen because there are 86,400 seconds in 24 hours.'' [emphasis added EM]
Livio Stecchini, “Notes on the Relation of Ancient Measures to the Great Pyramid” in Appendix to Secrets of the Great Pyramid by Peter Tompkins, pages 371-375, 378. Copyright to the Appendix is 1971.