Airborne Vector Gravimetry Theory And Methods

Airborne gravimetry system is very accomplished in obtaining the mid-high frequency information of the earth's gravity field. After our airborne scalar gravimetry system CHAGS (Chinese Airborne Gravimetry System) was successfully created, the research on airborne vector gravimetry is putting on agenda. Successful tests and practical survey have been clone at abroad in order to obtain 3D gravity field information. However, we have some gaps in this area because of our late starting; therefore we must fasten the research on the airborne vector gravimetry system. The main work is summarized as follows:The power spectral expression in terms of global mean disturbing gravity as well as its propagation features based on the spectral analysis theory of the gravity field is presented. A theoretical research is made on the capability of the detection of mid-high frequency information of the gravity field using airborne gravimetry.The mathematic model of vector gravimetry is deduced from the second motion law of Newton within inertial frame, according to which a basic principle of computing vector gravity using position and velocity information deduced from strap-down INS and GPS is described.The two sub-systems composing of airborne vector gravimetry system are discusseded in detail, which are strap-down inertial navigation system (SINS) and global positioning system (GPS). The effects caused by main error sources of these two sub-system are analyzed in detail according to the error equation of vector gravity, and a conclusion that SINS's errors mainly influence the low-frequency signals of vector gravity while GPS's errors mainly influence the high-frequency signals is drawn. The resolution of airborne vector gravimetry is analyzed according to the error spectrum and some conclusions useful for the flight are drawn.The cumulative errors caused by gyro drift are weakened by the Kalman filter, and two main methods are introduced, viz. Kalman filter based on the updates of positions and Kalman filter based on the updates of accelerations. Some simulated data are used to test the two methods.The applications of vector gravity on the determination of the earth's gravity field are described, including the downward continuation of vector gravity and determination of the local geoid.