STATUS OF WORLD GRAVITY STUDIES CONDUCTED BY WOODS HOLE OCEANOGRAPHIC INSTITUTION AND PRESENT PROBLEMS IN GLOBAL GRAVITY MEASUREMENTS
WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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Recent activity in the making of gravity measurements is directly related to the development of suitable portable gravity instruments that have both high range and precision which can be read rapidly, and a fuller realization of the application of gravity studies to the solution of fundamental problems in geodesy and geophysics. To successfully utilize the gravity data, the observations must be refferred to the same datum and must conform to a fixed standard of accuracy. The basis of calibration used in establishing the gravimeter constants employed in the world network was a series of check observations against the Cambridge University England pendulums. However, the absolute gravity values obtained with such calibrated instruments appeared to be questionable because of incomplete compensation for the effects of the earths magnetic field on these pendulums. The lack of an international gravity standard suitable for calibrating gravity measuring instruments is the primary difficulty associated with making long distance measurements involving changes of 1000 mgals or more. Similarly, no standard method is used to calibrate gravimeters, nor is there any uniformity in either the method of determining instrumental drift or in applying closures incorporating both drift and jumps introduced in readings by sudden shocks. A record should be submitted to a central agency indicating the field procedures used, the characteristics of the instrument, and the method of closure adjustment so that the data can be evaluated on a relative basis with other data.