Improving DGPS Accelerations for Airborne Gravimetry: GPS Carrier Phase Accelerations Revisited

Abstract

As airborne gravimetry matures as a technology, the major challenge remaining is to improve the accuracy and resolution of the measured gravity field. Errors in DGPS derived accelerations used for motion compensation are one of the main limitations. The standard method of determining aircraft acceleration is time differentiation of DGPS positions. In an effort to improve the quality of aircraft accelerations, an alternative method of deriving accelerations from DGPS is evaluated. The method, which was first presented by Jekeli (1994), estimates acceleration directly from GPS carrier phase measurements. It is revisited, with modification, and results in the gravity domain are presented for the first time. The carrier phase method is modified to utilize a least squares solution with a covariance model, to include all satellites available for a flight line. Using data from a strapdown airborne gravimetry campaign, gravity disturbance are estimated for the same input data with both the standard and modified carrier phase approaches. The results are compared and the,effect of the carrier phase derived accelerations is shown. To assess the accuracy, results are compared to an upward continued reference field. The modified carrier method is shown to improve the estimated gravity disturbances, especially under turbulent flying conditions and during times of higher atmospheric activity. The results are discussed with respect to the requirements of exploration geophysics.