The 360 isn't arbitrary, rather boils down to 60 arc-minutes and 60 arc-seconds, which of course is 3600 arc-seconds in circle. Where the 60 comes from: http:

The 360 isn't arbitrary, rather boils down to 60 arc-minutes and 60 arc-seconds, which of course is 3600 arc-seconds in circle. Where the 60 comes from: http://mathforum.org/library/drmath/view/65468.html http://mathforum.org/library/drmath/view/65468.html Wouldn't surprise me if the minutes and seconds relates to navigation time in the past.