Strapdown Gravity Disturbance Vector Determination Method Based on Error-Coupled Constraints and Direct Differencing-Optimal Estimation Synergy

This paper proposes a strapdown gravity disturbance vector (GDV) measurement method based on error-coupled constraints and direct differencing-optimal estimation synergy. Through theoretical derivation and simulations, the coupling mechanism among horizontal attitude errors, accelerometer biases, and GDV is revealed. Building on this analysis, a mathematical model for GDV determination under coupling constraints is established. Incorporating stochastic process modeling of the GDV, a Kalman filtering-smoothing model is formulated in which EGM2008 low-frequency reference values and the preliminary GDV results obtained via direct differencing are assimilated, thereby realizing a synergistic fusion of the direct differencing and optimal estimation methods. These innovations are integrated into a stepwise error separation strategy, yielding a comprehensive strapdown GDV measurement scheme. Airborne gravimetry experiments demonstrate internal consistency accuracies of 1.30 mGal, 0.80 mGal, and 0.44 mGal for the eastward, northward, and upward components respectively, with a spatial resolution of 4.8 km. The method significantly enhances separation capability between systematic errors and GDV, yielding marked improvements in horizontal components measurement precision.