Research On Relative Positioning Stochastic Model Of Combined GPS/BDS System

In recent years,with the rapid development of the satellite navigation systems, multi-system facilitates the development of GNSS navigation positioning system to the trend of more accurate, security and reliable.It is necessary to determine the stochastic model of the different kinds of observation when the combined system is used to relative positioning. In this context, the stochastic model of combined GPS/BDS relative positioning is studied for the purpose of improving the accuracy and reliability of combined GPS/BDS relative positioning. The main contents are as follows:1. The stochastic model of GPS/BDS static relative positioning.The accuracy of carrier phase observation that come from GPS and BDS is different because of the difference of the two systems.It will get the wrong result that if the weight matrix of observation in the process of adjustment is inaccuracy.For the some reason,the standard of least squares will lost its original meaning. To solve this problem,the combined GPS/BDS carrier phase observation is adjusted at the beginning.According to the observation residual of initial adjustment,the posterior variance estimation is used to determine the weight matrix of combined GPS/BDS carrier phase observation. The results show that this method improves the accuracy and reliability of the GPS/BDS carrier phase baseline solution.2.GPS/BDS single epoch relative positioning. The pseudo-range observation is introduced to improve the situation that observation equation is rank deficient When only use the phase observation to get single-epoch baseline solution. So there are different types of observations which come from different systems. In the past, the common observation stochastic models are empirical model, stochastic model based on the height angle and stochastic model based on the signal strength. The posteriori estimation method that redefining the stochastic models of different types of observations which come from different systems accord to the correction of pre-adjustment is used in this article.3. The effect that observation stochastic model on ambiguity searching in GPS/BDS single epoch relative positioning. The single epoch success ambiguity searching rate and accuracy of baseline fixed solution are analyzed when the unit weight matrix, elevation model, the signal strength model and the posterior variance estimation model respectively used.