Effective measurement height of atom gravimeters
  The effective measurement heights of the fountain and the release types of atom gravimeters have been determined using the description of the instruments as linear time-invariant (LTI) system. The distance from the initial position of the atoms to the locus of the effective measurement height is expressed as simple fraction of the total trajectory length. Leaving the measured gravity for reporting at the effective measurement height allows to eliminate the gradient from calculations and avoid up to 1 $\mu$Gal of its uncertainty added to the instrument error budget. 
V. D. Nagornyi
physics.ins-det physics.atom-ph physics.geo-ph