Data Processing And Stability Analysis Of High-level GNSS Surveying Control Network

With the gradual improvement of satellite navigation system and the rapid development of satellite navigation and positioning technology,related engineering applications and infrastructure construction have put forward higher requirements for high-precision baseline calculation.Among them,GAMIT software has been widely used in high-precision GNSS baseline calculation due to its features of high precision,high efficiency and open source code.GAMIT software provides six different baseline resolution types and several types of processing tuning parameters.In order to explore the influence mechanism of different solving strategies and parameter Settings on GNSS baseline solving accuracy,this paper mainly carried out experimental verification from the following aspects.(1)for satellite as high Angle setting influence on calculating results,the Hong Kong CORS station observation data for 10 days,respectively,to normalized root mean square,baseline repeatability,baseline error statistics,the results showed that the increase with the gradually by the high Angle,NRMS values decrease gradually,but are within 0.2,and the baseline error increases gradually;When the cut-off Angle is 15°,the baseline error is 0.42cm;when the cut-off Angle is 20°,the baseline error reaches 0.7cm.Therefore,it is more appropriate to set the cut-off Angle as 10°?15°.When the multi-path effect of the test station is serious,the cut-off Angle can be appropriately increased,but it should not exceed 20°.(2)A detailed experimental analysis was made on the prior coordinates and constraints of the measurement station.The results showed that the prior coordinates obtained from the observation file header had a higher precision of solution.At the same time,a higher precision could be obtained if the error of prior coordinates was within 30m.The constraint value of the test station and the number of constraint points have an important influence on the solution,and the constraint value is related to the accuracy of approximate coordinates.When there are control points with poor data quality,3?4 control points in the network can be strongly constrained to obtain better solution results,but the number of constraint points should not exceed 5.(3)Different baseline lengths are applicable to different types of baseline solutions.L1_ONLY,L1,L2_INDEPENDENT are only applicable to precise baseline solutions below 5km.When there is a large difference in baseline lengths in the control network,better adjustment values can be obtained after separate solutions.Taking the plane control network of Humen Second Bridge in Guangdong province as an example,the application of GAMIT software in the high-precision GNSS engineering control network is systematically elaborated.For each control point,the stability of two adjacent phases is analyzed by using The F-distribution and T-distribution,and the parameter setting characteristics of GAMIT software are summarized,which has certain reference significance and engineering practical value.