Re: Complications
g (ie GM) is involved because the standard clocks are corrected for General Relativity to mean sea level. It being slightly impractical to run all the atomic clocks in completely flat spacetime. Can't remember if the second was defined at msw or the clocks are simply corrected to msw before being compared.
Standard atomic clocks are so accurate that you use them to define the geoid height at the lab, which you then use to correct each clock when they are compared - it is a slight chicken-egg problem.
Biting the hand that feeds IT
