A Comparison Between Three IMUs for Strapdown Airborne Gravimetry

摘要

Strapdown airborne gravimetry relies on the combination of an inertial measuring unit (IMU) and a global navigation satellite system (GNSS) to measure the Earth's gravity field. Early results with navigation-grade IMUs showed similar accuracies to those obtained with scalar gravimetric systems in the down component. This paper investigates the accuracy of three IMUs used for strapdown airborne gravimetry under the same flight conditions. The three systems considered were navigation-grade IMUs, iXSea AIRINS and iMAR iNAV-FMS, and a tactical-grade Litton LN-200. The data were collected in 2010 over the Island of Madeira, Portugal, in the scope of GEOid over MADeira campaign. The coordinates and orientation of the aircraft were computed using an extended Kalman filter based on the inertial navigation approach. GNSS position and velocity observations were used to update the filter, and the gravity disturbance was considered to be a stochastic process and was part of the state vector. A new crossover point-based serial tuning was introduced to deal with the uncertainty of choosing the filter's a priori information. The results show that with the iXSea accuracies of 2.1 and 1.6 mGal can be obtained for 1.7 and 5.0 km of spatial resolution (half-wavelength), respectively. iMAR's results were significantly affected by a nonlinear drift, which led to lower accuracies of 4.1-5.5 mGal. Remarkably, Litton showed very consistent results and achieved an accuracy of about 4.5 mGal at 5 km of spatial resolution (half-wavelength).