Research On GNSS Carrier Phase Dynamic Velocity Measurement Model Under Partially Shaded Condition

Velocity plays an important role in the navigation and positioning system.With the development of the times,conventional velocity measurement technology can no longer meet people's needs.High-precision carrier phase time differential velocity measurement is favored by Chinese and foreign scholars.If it is in a complex urban environment,this method is no longer applicable.In order to solve this problem,the paper studies the carrier phase time differential velocity measurement and its accuracy.The main contents and results are as follows:(1)The principle and algorithm of GPS carrier phase time differential velocity measurement are studied.On the one hand,the influence of error on the velocity measurement result is studied from the error source that affects the velocity measurement result.The result shows that the influence of error source on the velocity measurement result is mm/s level.On the other hand,in order to evaluate the accuracy of the velocity measurement results,they were evaluated from both static and dynamic aspects.The results show that in the static state,the true value of the velocity is zero,and the accuracy of the velocity measurement reaches the mm/s level.In the dynamic state,the true value is easy to obtain,so the velocity measurement result of the IE commercial software is used as the reference value,which can be obtained through comparative analysis.Knowing the velocity accuracy can reach the cm/s level.(2)Through the research on the velocity measurement model,the single system velocity measurement model is deduced to the multi-system velocity measurement model,and the velocity measurement of GPS,BDS,GPS/BDS and GPS and BDS different types of satellites are compared and classified.The GPS/BDS combination can effectively improve the geometrical state of the satellite space,and the velocity measurement error is significantly reduced,but it is more fluctuating than the GPS,which may be due to the large error of the received BDS data.After that,different types of BDS satellites are integrated with GPS,It is found that the GEO/IGSO/MEO Beidou satellite can effectively enhance the stability of the speed measurement and improve the accuracy of the speed measurement.(3)It is studied that when the receiver receives only three GNSS satellites,the geodetic-assisted positioning algorithm is added,and the positioning accuracy of 10 m can be obtained by using GPS,BDS and GPS/BDS in a short time.After that,the important principles such as the principle and algorithm of GNSS carrier phase time differential velocity measurement in incomplete conditions are studied.The GPS,BDS and GPS/BDS can maintain the accuracy of the velocity measurement in the east,north and sky directions respectively.At the dm/s level.(4)In further research,it is found that based on the Samsung GNSS carrier phasedifferential velocity measurement model,by adding the binomial fitting model,the velocity prediction can be solved under the condition of double-star,single-star and satellite full-shadowing,GNSS satellite situation.Next,the velocity information of the receiver.Through experimental analysis,the binary GNSS carrier phase differential velocity measurement can be obtained.The GPS,BDS,GPS/BDS can obtain the dm/s velocity measurement accuracy within60 s,and the precision retention time is short.It can only maintain 60 s,and the excess error is rapidly increased.Single-star velocity measurement and velocity prediction under satellite full-shielding conditions,although the carrier velocity can be calculated in 60 s,only a short-term uniform motion can be calculated.For variable-velocity motion,a better velocity value cannot be calculated and the constraint condition is lacking.