Determining The Position, Velocity & Acceleration Using GPS In Airborne Gravimetry

The airborne gravimetry is one of the geophysical prospecting methods which has been developing quickly and deeply in recently years. It is the gravity measurement technology that takes the airplane as the carrier, which is superior to ground gravity measurement. First of all, it can fast, economically and flexibly perform a task with high accuracy. For another, it can work in the district where human rarely reach, such as desert, marsh, high mountain, and so on. One of the key problem which airborne gravimety has to solve is how to separate the disturbing accelerations, which is generated by aviate, from the total acceleration which is observed by gravimeter. Using the differential GPS technology, we can get the position, velocity, acceleration and any other parameters of the aircraft carrier in high accuracy which can be used to make the necessary correction of the total acceleration. This dissertation focuses on how to solve the problems of the airborne gravimetry with DGPS technology. The follows are the main points of the dissertation :The dissertation presents the requirements of airplane position, velocity and acceleration on the basic theory, mathematical model and the error propagation law of the airborne gravimetry, which can be solved by making use of GPS data. In addition, the dissertation introduces coordinate system, time system and how to shift between them, which are involved in GPS data processing.In order to determine the time, position, velocity and acceleration of airplane, it is the fist step to determine the position, velocity and any other orbit’s motion parameters of the GPS satellite. The dissertation describes the theory and calculation steps in WGS-84 coordination system by using the broadcast ephemeris, and also gives the method of converting to the carrier coordination system, which make the GPS antenna as the coordination origin. Finally the author of the dissertation uses Chebyshev polynomial interpolation and outputs the epoch sequences data of GPS satellite motion parameters consist with sample time series of GPS observation files.This dissertation illustrates how to use pseudorange, carrier phase and Doppler frequency to compute the velocity, and acceleration (10 dimensions state vector) of the airborne. For the purpose of acquiring the optimal value, the dissertation discusses the design of digital filter which include time filter, space filter and Two-D filter break, which are applied to eliminate interferences which are mainly caused by measurement noises; and then the dissertation also considers applying the least-square and Kalman filter optimal estimation theory to approach true value. It only can get the appropriate processing parameters by repeated trial in most practical applications.The author of the dissertation also develops GPS post-processing software system software for airborne gravimetry, which is called EG2010, based on the concept of software architecture. In the concept of software architecture, the software is the integration of different functional components according to certain interactive mode. Furthermore, the user can deal with GPS data processing with more imaginations in the future versions.In the last place, the dissertation presents the processing results of actual airborne gravimetry GPS data using EG2010. And by the comparison with the software of the GT-1A made in Russia, we can get the conclusion that EG2010 has basically met the requirement of airborne gravimetry for GPS processing.