Gravity is not a constant and that would probably matter at the precision that needs to be measured in the given test environment. In any other situation, gravity (or the state of the earths magnetic field) absolutely would not matter.

The precision of F=MA might even be debatable as an accurate formula at these scales… I dunno about that though.

en.m.wikipedia.org/wiki/Gravity_of_Earth

…nasa.gov/…/measuring-earths-magnetism