Airborne Gravity Surveys Over Taiwan Island and Strait,Kuroshio Current and South China Sea: Comparison of GPS and Gravity Accuracies at Different Flight Altitudes

We compare the accuracies of GPS and gravity observations obtained from three airborne gravity surveys over Taiwan Island at altitude 5000 m and over Kuroshio Current, Taiwan Strait, and Dongsha Atoll at altitude 1500 m. A kinematic network adjustment was used to determine the positions of the aircrafts. GPS positioning errors are at the decimeter-level, which are not entirely propagated to velocity and acceleration errors due to cancellation of long wavelength errors. Outliers are downweighted in the Gaussian filtering to improve the gravity accuracy, especially at altitude 1500 m. Compared with the upward-continued gravity, the gravity anomalies from the 1500-m surveys show a consistent accuracy of about 3 mgal; the accuracy from the 5000-m survey is degraded, especially over high mountains. The RMS crossover differences at 1500 m and 5000 m are all below 3 mgal, suggesting flight altitudes do not affect the crossover difference. Coherence analysis suggests that the spatial resolvable wavelengths of the airborne gravity range from 4 km (altitude 1500 m) to 6 km (altitude 5000 m).