| CPIII control network is the positioning benchmark at the stages of high-speed railway construction and operation,and it is also the basic guarantee of high smoothness and stability of the line.Its field data acquisition speed directly affects the efficiency of high-speed railway construction and maintenance.Especially in the operation stage,the time that each line leaves to the inspectors every day is only 4 hours in the morning,which requires the CPIII control network to retest as quickly as possible under the premise of ensuring the accuracy.CP? control network includes plane control network and elevation control network,and precise digital level is used for field data collection of elevation control network.The efficiency of leveling mode is low and the work intensity is large,which seriously affects the speed of field data acquisition of CP? elevation control network.As far as a CPIII control network is concerned,its plane control network and the elevation control network use the same control points,if the vertical angles and oblique distances of the CPIII plane control network can be used to construct the CPIII precise triangular elevation control network for the purpose of replacing the traditional CPIII precise leveling network,synchronous data acquisition of CPIII plane control network and elevation control network may be achieved,and the measurement speed and efficiency of the CPIII control network can be improved greatly.However,the accuracy of trigonometric leveling is far lower than that of precise leveling due to the systematic errors such as atmospheric refraction,earth curvature and vertical deviation.Among the above error sources,atmospheric refraction is affected by the temperature,humidity,air pressure and other environmental factors on the line of sight,which has the greatest impact on the observation value of precision trigonometric leveling,and there will be random changes in the observation process.Eliminating the influence of atmospheric refraction is the key to improve the accuracy of CP? Precise Trigonometric Leveling Control Network.In this paper,in view of the large amount of data in CP? Precise Trigonometric vertical control network,the influence of systematic deviation is eliminated by introducing the parameters to be calculated into the adjustment model,and the parameter matrix is optimized by using mathematical statistics method.At the same time,aiming at the problem of multiple types of original observation values,the Helmert variance estimation method and the minimum norm quadratic unbiased estimation method are used to Carry out strict weight determination.The research contents and innovative achievements of this paper are as follows:(1)The factors affecting the precision of CP? precise trigonometric leveling control network are studied.The simulation results show that the main error sources are the influence of atmospheric refraction and earth curvature,followed by angular error and vertical deviation.Under the condition of only accidental error,the mean square error of height difference between adjacent CP? points can reach the level of 0.2mm.(2)The adjustment model of CP? Precise Trigonometric Leveling Control Network with parameter method is proposedThe influence of atmospheric refraction and earth curvature is solved by introducing parameters to CP? Precise Trigonometric Height observation equation.Aiming at the situation that the atmospheric conditions of adjacent stations do not change significantly,the optimization method of spherical air difference parameter matrix is proposed,which avoids the excessive parameter of adjustment model and reduces the calculation accuracy.Using this model to construct CP? elevation control network,most CP? precise trigonometric leveling control network can fully meet the requirement that the mean square error of height difference between adjacent points is less than 0.5mm.(3)Two methods are proposed to weaken the influence of vertical deviation in CP? Precise Trigonometric Leveling Control NetworkWhen the variation of the vertical deviation in the survey area is linear,the influence of the variation of the vertical deviation is eliminated by introducing the variation coefficient of the vertical deviation into the adjustment model;when the variation of the vertical deviation in the survey area is complex,a small number of precise leveling observations are introduced in sections,the variation coefficient of the vertical deviation in each section is inverted,and then the vertical deviation of the precise trigonometric elevation observations is corrected.It can be seen from the experiment that the results of the two methods are consistent,and both of them can weaken the influence of the variation of the vertical deviation.(4)The problem of tight weight determination in CPIII precise trigonometric elevation control network has been studied.In the data processing of CPIII precise trigonometric elevation control network,the original observation values include oblique distance,vertical angle and a few precise leveling observations.In high-precision data processing,strict weighting must be considered.Through theoretical analysis and calculation of measured data,it is found that in the CPIII control network,because the vertical angle is very small(the vertical angle is usually less than 2 degrees),the influence of ranging error on the elevation control network can be neglected,so when the original observation value is only vertical angle and oblique distance,no strict weighting is needed.(5)The adjustment of CP? Precise Trigonometric vertical control network with the participation of some precise leveling observations has been studied.The precision of the precise leveling observation value is much higher than that of the Precise Trigonometric Leveling observation value,so it is helpful to introduce some precise leveling observation values into the CP? Precise Trigonometric Leveling Control Network in theory to improve its solution.In the joint adjustment,in view of the fact that the line of sight is close to the horizontal in the process of CP? control survey,it is found through analysis and test that the height difference accuracy of adjacent CP? points is the highest when the precise trigonometric elevation observation value and precise leveling observation value adopt the distance weighting.However,the weight ratio relationship between the two types of observations needs to be determined by Helmert model variance estimation method.Through the comparison of the calculation results of various test schemes,it is found that the number of inspection conditions made up of the observation values is the key factor affecting the precision of strict weight determination.(6)The adjustment method of CP? three-dimensional control network based on bursa model is proposedIn view of the difficulty of constructing the line leveling network in the high altitude area,this paper proposes a CP? three-dimensional control network adjustment model based on the bursa model.This method uses GNSS technology to provide three-dimensional datum,processes the data in the geocentric coordinate system,and carries out the point location sampling in the station coordinate system,which can completely get rid of the limitation of leveling mode on the construction of high-speed railway control network. |
PDF Full Text Request