4TH INTERNATIONAL COMPARISON OF ABSOLUTE GRAVIMETERS

In 1994, from 24 May to 8 June, the fourth International Comparison of Absolute Gravimeters was held at the Bureau International des Folds e t Mesures, Sevres, France. Eleven absolute gravimeters were operated a t five sites and then compared by means of a high-precision gravity ne twork which was itself observed throughout the period. The results dem onstrate that absolute, gravimetry can be carried out to an accuracy o f 3 mu Gal to 4 mu Gal, which represents a substantial improvement sin ce the first international comparison (1981, 10 mu Gal). The relativel y low rate of improvement, one third of an order of magnitude in fifte en years, is certainly limited by current technology for measuring sma ll time and space intervals. A notable finding of the comparison was a n unsuspected source of systematic error which can be eliminated by ne w hardware or corrected through a correction algorithm.