Abstract: Due to the change or damage of the survey points, the precision of the oriented boundary surveyed can not meet the requirements of relevant standards, or the oriented boundary disappear. Under such circumstance, nonoriented traverse surveying technology may be used. The calculation methods and precision of nonoriented traverse are presented, and the application of nonoriented traverse in the survey of Guangzhou Metro is discussed. Conclusions drawn are as follows: 1) The error induced by direction changing of oriented boundary can be reduced by using nonoriented traverse. 2) The nonoriented traverse surveying method is an effective method, which has high precision in shield orienting. 3) The nonoriented traverse surveying method can improve the relative precision of control points in the breakthrough survey of running tunnel.

Key words: Guangzhou Metro, nonoriented traverse, survey precision