A comparison of stable platform and strapdown airborne gravity

To date, operational airborne gravity results have been obtained using eith er a damped two-axis stable platform gravimeter system such as the LaCoste and Romberg (LCR) S-model marine gravimeter or a strapdown inertial navigat ion system (INS), showing comparable accuracies. In June 1998 three flight test's were undertaken which tested an LCR gravimeter and a strapdown INS g ravity system side by side. To the authors' knowledge, this was the first t ime such a comparison flight was undertaken. The flights occurred in Disko Bay, off the west coast of Greenland. Several of the flight lines were part ly flown along existing shipborne gravity profiles to allow for an independ ent source of comparison of the results. The results and analysis of these flight tests are presented. The measurement method and error models for bot h the-stable platform and strapdown INS gravity systems are presented and c ontrasted. An intercomparison of gravity estimates from both systems is giv en, along with a comparison of the individual estimates with existing shipb orne gravity profiles. The results of the flight tests show that the gravit y estimates from the two systems agree at the 2-3 mGal level, after the rem oval of a linear bias. This is near the combined noise level of the two sys tems. It appears that a combination of both systems would provide an ideal airborne gravity survey system, combining the excellent bias stability of t he LCR gravimeter with the higher dynamic range and increased spatial resol ution of the strapdown INS.