A Study Of The Orbit Determination Of GPS Satellite Using Zero-Difference Observation

The orbit precision is an important factor to judge the quality of satellite navigation system. The thesis makes a deep research on orbit determination of GPS satellite using Zero-difference observations, and the source of the observations are from CMONOC and IGS tracking data .The main work is summarized as follow.1. The orbit fit method is used to fit orbit parameters and then the motion equations and variational equations are solved by means of Collocation method which is a numerical integration method. A method of test the validity of integration method is advanced, and in this way Collocation method is tested to be in effect.2. The mathematic model of orbit determination of GPS satellite using zero-difference data is deduced in detail. Then the pre-processing of GPS zero-difference observation data is studied. An automatic editing algorithm for zero-difference data is employed to effectively reject outlier and to detect then mark cycle slips. The magnitude of all kinds of error of zero-difference data is estimated through computation.3. The method of block adjustment is employed to estimate parameters. The method of parameters elimination is introduced to eliminate the receiver clock error and the satellite clock error, accordingly, the dimension of normal equation is reduced effectively. The causes of rank defect of normal equation are analyzed, and then the problems are solved by advancing different method to different causes.4. The effect of arc length on orbit determination is studied. The results show that after the arc length increases to an extent, the orbit precision is nearly not improved through increasing arc length again.5. The effect of data quality on orbit determination is studied, the results show that the shorter the arc length is, the bigger the effect of data quality acts on precision of orbit determination.6. The effect of the error of reference orbit on orbit determination is studied, the results show that although adding an error of magnitude of 100 meters, the effect on orbit determination is very little.