New Methodology for Stability Analysis on Repeated Measurement of CPⅢ Vertical Control Network

In the current code on the stability analysis of repeated measurements for the CPⅢ vertical control network of high-speed railways, the divergence tolerance of elevation between original and repeated measurements should be no more than 2 mm, which is not reasonable due to misjudging stable points. Besides, there is also poor evidence to set the altitude difference between original and repeated measurements to be no more than 3 mm. Thus, more reasonable divergence tolerance of elevation and altitude difference between the original and repeated measurements were deduced, and a new method on the stability analysis of CPⅢ vertical control network was proposed. This new method calculates the altitude difference for every segment of the CPⅢ vertical control network and detects unstable segments in the whole network according to the original and repeated measurement limits. Then, for the two CPⅢ points on each unstable segment, the divergence tolerances of elevation were computed respectively to detect the unstable CPⅢ points of the unstable segments and analyze the stability of CPⅢ vertical control network. Both the theoretical and test data show that when the divergence tolerance of elevation between original and repeated measurements for the neighboring points is less than 1.4 mm, the proposed method can reliably detect the unstable points from the CPⅢ vertical control network.