The distance between two pillars whose latitudes differed by 1 degree in a north–south direction was measured using sighting pegs along a flat desert plane.
If al-Farghani used the legal cubit as his unit of measurement, then an Arabic mile was 1,995 meters long.
[2] Around 830 AD, Caliph Al-Ma'mun commissioned a group of Muslim astronomers and Muslim geographers to perform an arc measurement from Tadmur (Palmyra) to Raqqa, in modern Syria.
They found the cities to be separated by one degree of latitude and the corresponding meridian arc distance to be 66⅔ Arabic miles and thus calculated the Earth's circumference to be 24,000 miles (39,000 km).
[3] Using this measurement, knowing that earth's circumference is 40,007.683 km makes the Arabic mile little more than 1,666.994 metres.