Abstract
Using the precision trigonometric elevation instead of the precision levelling to build a CPⅢ elevation control network will greatly increase the speed of CPⅢ control network construction. However, the accuracy of CPIII precision trigonometric elevation control network is still difficult to reach the level of CPⅢ precision levelling network. Based on the existing parameter method, this paper introduces some precision levelling for joint adjustment, and uses Helmert’s variance estimation method to perform strict weight determination. Our experiments show that when the number of precision levelling participating in the joint adjustment exceeds 1/3 of the total number of CPⅢ precision levelling network observations, the accuracy of the CPIII precision trigonometric elevation control network can be effectively improved.
Highlights
A CPIII control network includes a plane control network and an elevation control network, which is the position reference for the construction and operation stages of high-speed railways
The trigonometric elevation observations are affected by systematic errors such as atmospheric refraction, earth curvature, and vertical deviation
References [1,2,3,4,5] adopted the observing method to eliminate the influence of atmospheric refraction and the curvature of the earth in the trigonometric elevation observations, so that the precision of the precise trigonometric elevation measurement reached the national second-class requirements
Summary
A CPIII control network includes a plane control network and an elevation control network, which is the position reference for the construction and operation stages of high-speed railways. Because the level measurement mode is inefficient, it is a challenges as to how to improve the efficiency of CPIII elevation control network data collection in the current construction of high-speed railway control network. References [1,2,3,4,5] adopted the observing method to eliminate the influence of atmospheric refraction and the curvature of the earth in the trigonometric elevation observations, so that the precision of the precise trigonometric elevation measurement reached the national second-class requirements. From the calculation of a large amount of measured data, it is found that the probability of gross errors in precision trigonometric elevation observations is much higher than the precision levelling These gross error observations have a serious impact on the control network. It is proved that introducing a certain number of precision levelling can effectively improve the accuracy of the CPIII precise trigonometric elevation control network; but if the number of precision levelling is insufficient, it will lead to the failure of strict weight determination
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