Integrated Carrier Phase and Doppler Observations of GPS and GLONASS for Precise Velocity Determination

In order to overcome the disadvantages of existing GNSS velocity determination methods, a comprehensive method is developed in this paper, where the raw Doppler and virtual Doppler data derived from GPS and GLONASS carrier phase observation are used. The basic idea is as follows: firstly the virtual Doppler data is obtained by using differential carrier phase observation, and an approach for the choice of the best point number of central difference method is discussed; then the different types of observation data are fused by adding their normal equations; and their weights are evaluated by the strict Helmet variance component estimation. To control the influence of outliers, the bifactor equivalent weights strategy is adopted. To verify the validation of this method, the airborne and carborne GNSS data are tested. The results show that the proposed method can improve the precision of velocity determination compared to the method of only using the raw Doppler, and can reduce the effects caused by sudden change of vehicle status compared to the method of only using the virtual Doppler. Additionally, the stability and reliability of resolution can also be further improved by combining GPS and GLONASS data.