Research On Accuracy Evaluation Method Of Mobile RTD Based On CORS

CORS is a higher evolution of GNSS application since the development of social economy and construction.It is a spatial information system that can acquire spatial data and geographical features quickly and accurately.The mobile RTD measurement based on CORS has the advantages of short positioning time and high efficiency,and the establishment of CORS has a significant improvement on the precision of pseudo range differential positioning.In this paper,aiming at the problem of mobile RTD based on CORS and its accuracy evaluation,and combining with the evaluation standard of CORS,a new error evaluation system is proposed.Taking Shaanxi Province as the research area,the accuracy of mobile RTD based on CORS is studied from two aspects of system error evaluation and user error evaluation.The main research contents and results are as follows:(1)In the system error evaluation,the pseudo range differential positioning technology can eliminate the common error.In this paper,static positioning accuracy test,multi-path effect test,communication link delay error test,data integrity test are designed to evaluate the system error.The results show that the effective measurements of the 45 reference stations selected in the multipath effect test are more than 85%,the MP1 and MP2 values are less than 0.5,the communication delay of the 45 reference stations selected in the communication link error test is kept at about 20 ms,and the maximum delay error is not more than 100 ms.The static positioning test obtains the static positioning coordinates of GPS,BDS two star fusion and single Beidou two modes The mean square error of observation points is±0.37 cm,±0.41 cm in x direction,±0.36 cm,±0.43 cm in y direction,±1.22 cm,±1.48 cm in h direction respectively.(2)In the user side error evaluation,this paper has carried out a variety of carrier,a variety of terrain mobile RTD test,using fixed baseline length detection method and fixed geometry track detection method two evaluation methods.The research results show that the fixed baseline length detection method can effectively detect the accuracy of mobile RTD in the long-time,large area and multi terrain test.The plane accuracy of the six selected mobile RTD test lines is better than 0.3 m,and the elevation accuracy is better than 0.6 m.The fixed geometry track detection method adopts the walking moving measurement method.When the tester passes through the fixed point,he will stay and observe for a period of time.The research result is that the positioning accuracy of the moving RTD is 0.262 m.When he stays at the fixed detection point,the positioning accuracy will be significantly improved,which shows that the positioning accuracy is greatly affected by the motion state.(3)In the vehicle borne RTD test,the plane accuracy of vehicle borne RTD in different terrain areas of mountain,plain and plateau is 0.26 m,0.2 m and 0.22 m respectively,which is obviously influenced by terrain factors,resulting in the lower test accuracy in these two areas.At the same time,due to the influence of road factors,the vehicle positioning accuracy of the high-speed route is better than that of the corresponding national road.In the ship borne RTD test,the plane accuracy of test line 1 and test line 2 is 0.17 m and 0.083 m respectively,and the elevation accuracy is 0.397 m and 0.215 m respectively.There are many mountains around test line 1,while the surrounding of test line 2 is mostly farmland and river beach.Influenced by the terrain factors,the ship borne positioning accuracy of line 2 is better than that of line 1.The comparison and analysis of vehicle borne and ship borne tests show that due to the wide water surface and less shielding,the ship borne positioning accuracy of line 2 is better than that of line 1 Therefore,the positioning accuracy of onboard RTD is better than that of onboard RTD.