On Barsoom the AD is the basis of linear measurement.
It is the equivalent of an Earthly foot, measuring about 11.694
Earth inches. As has been my custom in the past, I have generally
translated Barsoomian symbols of time, distance, etc., into their
Earthly equivalent, as being more easily understood by Earth
readers. For those of a more studious turn of mind it may be
interesting to know the Martian table of linear measurement, and
so I give it here:
10 sofads = 1 ad
200 ads = 1 haad
100 haads = 1 karad
360 karads = 1 circumference of Mars at equator.
A haad, or Barsoomian mile, contains about 2,339 Earth feet.
A karad is one degree. A sofad about 1.17 Earth inches.