| Accelerations derived from GPS are usually derived by twice time differentiating positions. In airborne gravimetry, the accuracy of accelerations obtained this way is limiting the achievable accuracy and resolution of the measured gravity field. Therefore, alternative methods of acceleration estimation need to be investigated. The current process, referred as the position method herein, has operation constraints, in addition to being unable to supply the desired accuracy.; An alternative method, referred to as the carrier method, is developed, implemented and evaluated. The carrier method estimates acceleration directly from the carrier phase measurements. A covariance model is developed and applied in the carrier method estimation process.; Testing is conducted using data from an airborne gravimetry campaign flown near Ottawa, Canada in the spring of 2000. An independent reference gravity field is available for the test area. Both methods of acceleration determination are used to estimate scalar gravity disturbances for approximately 720 km of flight lines.; Based on the analysis of the results, the carrier method offers a slight improvement (approximately 15% at 1.4 km resolution) in overall accuracy, as compared to the position method. In terms of robustness under operational conditions, the carrier method is shown to be better than the position method. Namely, positioning accuracies can be relaxed to the order of meters and changes in the visible GPS constellation do not adversely affect the estimated accelerations. |
