Fine analysis of lever arm effects in moving gravimetry

Abstract

A moving inertial gravimetric system is now being developed, consisting of three high precision accelerometers measuring accelerations along three non-parallel axes. The system has been designed to make high resolution gravity measurements on motor vehicles, ships or aircraft at mGal level of precision. Position, velocity and attitude of the platform, needed for computing acceleration corrections, are provided by a 4-antenna GPS system rigidly mounted on the platform with a sampling rate of 1 or 2 Hz. Because acceleration and GPS measurements are not made at the same point, the signals derived from the accelerometers have to be corrected for lever arm effect. To this end, we derived the complete relationship connecting accelerometer and GPS measurements. The correction for the lever arm effect requires the computation of seven acceleration terms. The amplitude of the lever arm effect depends not only on the lever arm length, but also on the platform attitude. Our own findings based on both simulations and real measurements suggest that some of the seven lever arm terms have to be considered to reach a few mGals precision for gravity. We present a reliable method to assess the precision that can be achieved for lever arm effect determination given the precision of attitude and lever arm measurements. © Springer-Verlag Berlin Heidelberg 2007.