Abstract：A non-contact digital close-range photogrammetric method is presented in order to overcome the difficulties in the deformation measurement of large-scale tunnel and underground structures. This method employs only non-metric digital camera and requires no control points. One can set camera station arbitrarily and the entire three-dimensional displacement of numerous monitoring points can be obtained simultaneously. Compared with those traditional methods to monitor displacement by convergence measurement devices or total station instruments，it has the advantages of saving time，providing large quantity of measurement information and operational safety. A test is conducted in an actual cavern to verify the accuracy of the photogrammetric measurement for assessing the applicability to deformation measurement in tunnels and underground spaces. A comparison of the photogrammetric measurements with the total station instrument results shows that the measurement accuracy for deformation is considerably good；and it is a promising technique for deformation measurement of structures. An outline of the test and reports how the technique is applied to practical underground projects are provided. Some experiences are also summarized.
