CROSSCORRELATION METHOD FOR EVALUATING AND CORRECTING SHIPBOARD GRAVITY DATA

Abstract

In shipboard gravity meter operation it is important to be able to evaluate the data and to make corrections if the gravity meter is not performing perfectly. These objectives can be achieved to some extent by (1) describing the ship motion with the terms of a power series in ship accelerations and velocities, and (2) using the crosscorrelations between these terms and observed gravity to evaluate performance and to obtain a corrected gravity that does not correlate with any of the power series terms. The method makes use of the simultaneity of the variations of observed gravity with those of the power series terms. The method is applied to some actual gravity data taken with a gravity meter that was not performing properly. The results show clearly the poor performance and indicate the cause. Computed corrections greatly reduce the noise in the results and give a systematic correction. Tests of the gravity meter after it was returned for repair confirm the results of the crosscorrelation analysis and show that the computed corrections are accurate.