GPS test of the local position invariance of Planck's constant
  Publicly available clock correction data from the Global Positioning System was analyzed and used in combination with the results of terrestrial clock comparison experiments to confirm the local position invariance (LPI) of Planck's constant within the context of general relativity. The results indicate that h is invariant within a limit of |beta_h|<0.007, where beta_h is a dimensionless parameter that represents the extent of LPI violation. 
James Kentosh and Makan Mohageg
gr-qc