THE USE OF DIFFERENCING TO ELIMINATE ENVIRONMENTAL-EFFECTS IN THE INTERCOMPARISON OF ABSOLUTE GRAVITY METERS

Conventional intercomparisons between absolute gravity meters are limi ted in accuracy by the difficulty of removing environmental signals, i ncluding effects such as Earth tides, ocean loading, and barometric pr essure loading. These error sources can be eliminated completely throu gh the use of exactly simultaneous measurements. Differencing techniqu es have been developed and tested which are capable of determining bot h the differential meter bias and the gravity difference between two n earby piers to an accuracy that is limited only by the instrumental no ise. Preliminary tests show that a comparison accuracy of 0.3 mu gal m ay be obtained in less than 400 drops, independent of drop interval (1 mu gal = 10 nanometer/sec(2)).