Research On Key Technologies Of BDS/GLONASS Combined Positioning System

With the rapid development of satellite navigation technology,the requirement of navigation positioning accuracy is becoming higher and higher by users.The single satellite system has the disadvantages of few visible satellites,poor positioning accuracy and incomplete coverage in some areas.The combined satellite system can avoid the problem of single satellite system.It can also break the monopoly of GPS to the market.At present,there are many studies on GDOP solution,satellite visibility analysis and star selection algorithm for single satellite system.At present,the receiver on the market can only deal with single satellite system signals,and the positioning calculation process of the combined satellite system is different from the single satellite system.Combined satellite system provides high precision positioning timing function,and also aggravates the receiver's calculation burden.The demand for the efficiency of the user is also increasing.Therefore,the research on high efficiency and high precision of the combined satellite system is also the key problem to be solved at present.This paper analyzes China's Beidou satellite navigation system and the Russian GLONASS satellite navigation system of the satellite orbit distribution system,basic composition,navigation message format,time coordinate system and space coordinate system.The time system and coordinate system of BDS and GLONASS are unified,this is the paving for the joint positioning of the BDS/GLONASS combined satellite system.On the basis of the above research,this paper derives the principle of the satellite pseudo range positioning,and analyzes the influence of GDOP on the positioning accuracy in this process.Satellite Tool Kit is used to solve the two-dimensional and three-dimensional spatial distribution maps of BDS and GLONASS.The GDOP distribution of single satellite system and BDS/GLONASS combined satellite system under 0 degree elevation limit,10 degree elevation limit and 20 degree elevation restriction is simulated and analyzed in Asia Pacific and non Asia Pacific region.The simulation results show that the BDS/GLONASS combined satellite system avoids the problems of large GDOP value and discontinuity of location under the condition of high elevation angle restriction of single satellite system.At the same time,a new method of calculating the minimum value of GDOP is proposed in this paper.The geometric distribution of the satellite when the minimum value of GDOP is obtained is derived in theory,and the actual inaccessibility of the traditional GDOP minimum value is verified.The study is helpful to the autonomous satellite orbit navigation.Finally,the Python software is used to solve the satellite visibility of three systems of BDS,GLONASS and BDS/GLONASS under the condition of 0 degree elevation,10 degree elevation and 20 degree elevation.The results show that the number of visible satellites in BDS/GLONASS is far greater than that of single satellite system,and the positioning accuracy is higher.In this paper,the traditional GDOP minimum selection algorithm and the largest tetrahedron volume selection algorithm are verified by simulation.These two algorithms have the disadvantages of large amount of computation and unstable results.On this basis,an improved star selection algorithm for combined satellite system is proposed.The algorithm has high location accuracy while reducing computation and is suitable for satellite selection.