| Precise satellite orbit is the basic elements to meet the user's high precision data processing requirements.Since 1993,analysis centers of IGS using the precise satellites data have been dedicated to research on principle and method of GPS orbit combination,in order to gain a higher accuracy and more stable orbit,the IGS M-GEX plan announced the corresponding GLONASS orbit in 1998.Due to the current development trend of multi-type and multi-GNSS system,and the accuracy of multi-GNSS system and multi-type satellite(especially GEO)characteristics are not consistent,which put forward to higher requirements for the orbit combination theory and method.Till now the IGS M-GEX has not announced multiple types of satellites orbit,and the research on Galileo,Beidou satellite orbit is still in the initial stage,so this paper mainly researches on GEO/IGSO/MEO orbit combination,which is of important significance.In this paper,the precise ephemeris from analysis centers of IGS and IGS M-GEX are selected to calculate GPS and Galileo combined orbit,and the observation period is from May 3 to July 11 of 2015;observation period of BeiDou satellite orbit is based on selection of observation period for the relevant data from March 9 to 22,2014.The contribution has compared the results with different satellite coordinate frame consistency correction methods,different calculation of analysis centers and satellites weighting methods;according to the special characteristics of GEO satellite orbit,URE weighting method is reduced to calculation.Main conclusions can be obtained as follows:(1)The accuracy GPS combined orbit is better using the analysis center station coordinates(Sinex)rotation parameters coordinate frame consistency correction method,using analysis center of rotation parameters correction accuracy is second,non coordinate frame consistency correction is the worst,in the observation period,three cases of results respresented by one-dimensional mean RMS compared with IGS reference orbit are respectively 0.579 mm,1.702 mm,1.950 mm and 5.956 mm,6.146 mm,6.165 mm compared with IGR orbit;seven parameters of three cases with IGS/IGR orbit are similar,the translation parameters and the scale factor is almost no difference,the rotation parameter difference using the coordinate correction method of center rotation parameters results is smaller,whose vaule is about 10 uas to 15uas,causing 2 mm deviation of orb it,the relative RMS value between analysis centers and combined orbit is about 11 mm to 15 mm.Galileo satellite orbit accuracy is similar when using the erp parameters to coordinate the frame coordinate correction or not,and the possible reason is that the orbit of Galileo is joined orbit determination by GPS satellite orbit,which can be regraded as consistency with the coordinate frame of GPS satellite,compared to the reference orbit one-dimensional RMS calculated by the residuals is 4.05 cm,since the accuracy is also little difference under the two conditions;the one-dimensional mean RMS of analysis centers named Com,Gbm,Grm,Wum are respectively 8.2 cm,11.7cm,6.5cm and 5cm,and analysis center orbit accuracy has improved.In the two cases,there is not much difference between the seven parameters of the frame between the center orbit and the combined orbit.(2)To ensure the premise of consistency in coordinate frame consistency correction method,and compare the difference of GPS combined orbit satellite precision in different ways,founding Sio has poor consistency of analysis rotation parameters and erp parameters before GPS week1807,the accuracy of combined orbit is poor with Sio,so the paper chooses whether or not to participate Sio and optimization three situation in total;after statistics orbit average RMS are respectively 1.568 mm,0.837 mm and 0.664 mm;difference of seven parameters with IGS reference orbit is very small,the scale factor is less than 0.001mm,the translation parameters 0.01mm,rotation parameters in about 5uas,which has little effect on the accuracy of orb it.According to the Galileo satellite orbit,it is divided into two kinds of situation which is Turn involved in or not.In the above two cases,satellite orbit of other analysis center compared to the reference orbit has little accuracy difference,since the one-dimensional mean RMS of Com,Gbm,Grm,Wum are 8 cm,11 cm,7 cm and 5 cm respectively,among which Wum orbit has the maximum difference around lcm;results calculated by five analysis centers named Com,Gbm,Grm Turn and Wum are better than four analysis center ones,the accuracy are respectively 4cm and 3.7cm.So giving the appropriate weight of the analysis center,and joining the analysis center Turn can improve the accuracy of combined orbit.(3)To ensure the optimization of the coordinate frame consistency correction method and analysis centers to participate GPS orbit combination,and compare the accuracy of GPS combined orbit with three weight methods,which found that the accuracy of using the methods of absolute deviation and variance factor weight are consistent,RMS of the results calculated by the three methods compared with IGS and IGR reference orbit are 0.579 mm,0.431 mm,1.865 mm and 5.511 mm,6.406 mm and 5.866 mm.And the RMS values of combined orbit with three methods are 4.221 mm,4.191 mm and 4.161 mm respectively.The results of seven parameters compared with IGS reference frame is similar,translation parameters DX,DY,DZ is 0.1 mm and 3 mm to 4mm,the scale factor is at 0.002mm,with URE weighting method rotation parameters are 3 uas to5 uas compared with the other two has almost 0.1 uas difference;and the difference compared with IGR is similar to the situation with IGS,the difference in translation parameters and the scale factor is small,the rotation parameter is about 2 to 3 times with first two methods;the frame difference between analysis centers and combined ones also have similar results and the RMS has consistency between 12 mm and 15 mm.The use of different methods to determine the weights of the Galileo satellite orbit has similar results,since the fitting precision is 37.129 mm and 36.669 mm with two methods,analysis centers of Com,Gbm,Grm,Tum and Wum orbit accuracy difference is very small,which are 48 mm,73 mm,11 mm,86mm and 69mm respectively.There is no difference in the seven parameters between center orbit and combined orbit in the two methods,which is consistent with the conclusion obtained by GPS satellite orbit(4)The Beidou satellite orbit using different analysis centers,with Com in the combination,combined orbit accuracy is better,more utilization analysis center to participate in,more reasonable weight of each analysis center and satellite is given,the better is the accuracy.The along,cross and radial side accuracy of GEO satellites are respectively 0.90 m,0.15 m,0.40 m,three dimensional accuracy is about 1 m,IGSO along,cross and radial side accuracy are respectively 10 cm,7 cm,6 cm,MEO along,cross and radial side accuracy are respectively 12 cm,6 cm,5 cm;three dimensional accuracy is about 14 cmFor the utilization of the Beidou satellite orbit:in different weighting method,high precision orbit consistency is obtained using the URE orbit weighting method results,conpared with the existing Beidou combined orbit precisioa GEO,IGSO and MEO of the seven day fitting arc of the three-dimensional RMS accuracy are 0.96 m,0.14 m and 0.14 m respectively,the boundary Discontinuity test of three dimensibnal RMS of the GEO,IGSO,MEO satellite are 1.90 m,0.35 m,0.42 m respectively. |
PDF Full Text Request