A Comparison of Stable Platform and Strapdown Airborne Gravity

To date, operational airborne gravity results have been obtained using either a damped two-axes stable platform gravimeter systems such as the LaCoste and Romberg (LCR) S-model marine gravimeter or a strapdown inertial navigation system (INS), showing comparable accuracies. In June of 1998 three flight tests were undertaken which tested a LCR gravimeter and a strapdown INS gravity system side-by-side. To our knowledge this was the first time such a comparison flight was undertaken. The flights occurred in Disko Bay, off the west coast of Greenland. Several of the flight lines were partly flown along existing shipborne gravity profiles to allow for an independent source of comparison of the results. This paper presents the results and analysis of these flight tests. The measurement method and error models for both the stable platform and strapdown INS gravity systems are presented and contrasted. The results of the flight tests show that the gravity estimates from the two systems agree at the 2-3 mGal level, after the removal of a linear bias. This near the combined noise levels of the two systems. It appears that a combination of both systems would provide and ideal airborne gravity survey system; combining the excellent bias stability of the LCR gravimeter with the higher dynamic range and increased spatial resolution of the strapdown INS.