Research methods: Taking the repetition survey for precise control of outside Nanliang-Taihang Mountain Tunnel as an example，the discussion is made on the influence on the error in penetrating tunnel by two results in this paper through making analyses of the corresponding baselines' distance and azimuth.
Research results: The biggest distance difference of corresponding baselines is 4. 3 mm，the azimuth is-2.36",and the influence on lateral penetration of the tunnel by measurement error is 33.1 mm，so the results of original survey can be used.
Research Conclusions: In the repetition survey for precise control of outside tunnel it can be verified whether the result of repetition survey meets the requirement of construction accuracy or not through making comparison of the distance with azimuth of corresponding baseline. The influence on lateral penetration of the tunnel by measurement error can be reflected by verification of corresponding baseline. The practice shows the comparison and analysis of corresponding baseline can avoid the complicated works in tunnel and ensure the safety and procedure of construction.
2007, Vol. 24 
