| With the gradual development and perfection of the global navigation system,the combined positioning of multiple systems is gradually emerging,and the demand for multi-navigation system integrated navigation and positioning is gradually increasing.The research of multi-system star selection algorithm can not be ignored.This paper is based on the principle of four existing satellite navigation systems,theoretical analysis of GPS,BDS and GALILEO three systems have better compatibility,and finally decided to study the multi-system star selection algorithm for GPS/BDS/GALILEO three-mode.In the research of the article,the theory of satellite navigation and positioning is first elaborated,and the relationship between GDOP value and satellite star selection is derived.Then the principles of the best shape method,the maximum vector-end tetrahedral volume method,the six-star star selection algorithm,the maximum determinant method,the minimum GDOP value method,and the existing star selection algorithm are discussed.The existing star selection algorithms are summarized and classified as:Star selection algorithm and other algorithms based on satellite spatial distribution characteristics.The process of selecting a star based on the spatial distribution characteristics of satellites is as follows:the determination of the top seat star and the selection of the base star group.Through theoretical analysis,the satellite selected by the two-dimensional convex splicing algorithm has the best pedestal constellation and the appropriate pedestal,but the article specifically analyzes that the stellar algorithm has room for improvement,so the article is for Graham scanning.Two-dimensional convex hull selection algorithm is used to improve the algorithm optimization.The top star selection process and Graham scanning process of Graham scanning two-dimensional convex hull selection algorithm are improved respectively.Finally,the combined data of GPS/BDS/GALILEO three-mode system demonstrates the feasibility and theoretical significance of the improved algorithm.The main work of the thesis is as follows:(1)Theoretical analysis of the system composition,time system and space coordinate system of the four integrated navigation and positioning systems GPS,BDS,GALIEO and GLONASS.The theory shows that GPS,BDS and GALILEO have better compatibility.The basic principle of satellite navigation and the method of satellite position calculation are theoretically analyzed,and concrete formula deduction and demonstration are made.At the same time,the article analyzes the characteristics of satellite navigation message data and the process of satellite positioning position resolution,and provides theoretical support for related experiments.(2)Analyze the principle of user location calculation and expound the definition of geometric precision factor GDOP,and analyze the relationship between GDOP value and satellite integrated navigation positioning accuracy.Firstly,the principles of the selected star algorithm are discussed in detail:the best shape method,the six-star star selection algorithm,the satellite elevation and elevation angle selection,the maximum vector-end tetrahedral volume selection algorithm,the two-dimensional convex-package Graham scanning method,and the star selection algorithm.The minimum GDOP value selection algorithm,fuzzy star selection algorithm and determinant star selection algorithm are used to analyze and compare the existing star selection algorithms.The existing star selection algorithm principles are discussed in detail and then classified into:satellite space characteristics selection.Star algorithm classes and other classes.The purpose of satellite space characteristic selection is to select the best satellite combination with the largest volume of space.By analyzing and comparing the base constellation selected by the two-dimensional convex package star selection algorithm in this algorithm,the largest base constellation will be constructed.Therefore,the subsequent research in this paper is a detailed analysis of the two-dimensional convex hull selection algorithm.(3)Firstly,the detailed principle of Graham scanning two-dimensional convex hull method is expounded,and the specific scanning process is analyzed.It is found that there are optimization and improvement of the top-seat selection process and Graham scanning process of the algorithm.The article designs and improves the two directions:First,for the selection problem of the top seat star in the two-dimensional convex hull Graham scanning method,the improved strategy of comprehensive satellite signal-to-noise ratio and satellite elevation angle selection of the top seat star is proposed.Based on the Graham scanning algorithm implementation and algorithm principle analysis,the satellite is preprocessed to reduce the Graham scanning method to scan the satellite,and the algorithm operation amount is reduced to realize the operation optimization.The article evaluates the optimization algorithm by GPS/BDS/GALILEO three-system combined navigation data.The positioning performance of satellite star selection results is improved by 10?20mm after the improvement of the top seat star.After the Graham scanning process is optimized,the number of single Graham scanning satellites is reduced.More than 2,the algorithm solution speed is increased by more than 0.004s.(4)The paper analyzes the application performance of Graham scanning two-dimensional convex hull selection algorithm under different system conditions,and selects the existing stars in the combination of GPS,GSP/BDS,GPS/BDS/GALILEO satellite systems.The algorithm six-star selection algorithm,eight-star best shape method,two-dimensional convex hull Graham scanning method and optimization algorithm are compared with the algorithm experiment.The performance of the algorithm is compared and analyzed by the algorithm result satellite number,GDOP value and algorithm positioning accuracy.The experimental comparison results show that under the single GPS system,the improved star selection algorithm does not improve the advantage.In the GPS/BDS dual system and GPS/BDS/GALILEO three systems,the improved positioning algorithm improves the positioning performance by 10?20mm,which proves that the comprehensive signal-to-noise ratio and satellite elevation angle are feasible for selecting the top star.The performance advantage of its optimization algorithm will be further expanded with the increase of the number of satellites in the combined system. |
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