Vector gravimetry by a combination of inertial and GPS satellite measurements

Vector gravimetry with inertial navigation systems (INS) has been successfully performed in semi-kinematic mode for several years. With advances in the kinematic use of the Global Positioning System (GPS), kinematic vector gravimetry has also come within reach. The problems of reducing the effect of INS sensor errors, determining the kinematic acceleration by means of GPS observations, and modelling the gravity vector in a state space setting are addressed. The requirements on INS and GPS observations are investigated in a covariance analysis. Different INS mechanizations, strapdown, platform, and rotating sensor unit are compared. It is shown that only the last two are suited for vector gravimetry. Subject to the principal limitations of the simulation study, the quantitative results show that current INS and GPS hardware should allow the determination of deflections of the vertical with an accuracy of 1 arcsecond. The determination of gravity anomalies with an accuracy of 10 micrometers per second squared, however, imposes very stringent requirements on the determination of the kinematic acceleration with GPS, which may possibly be met by high data rates and extensive filtering.