Research Of Camera Calibration And Control Point Layout In The Deformation Monitor Of Foundation Pit Of The Subway Line 2 In Hefei

With the development of urban construction, more and more cities are facing huge traffic pressure. In order to alleviate traffic pressure, to keep up with the rhythm of people’s lives and to speed up the urban development, the construction of rail transit project has become urgent. In the process of subway construction, in order to guarantee the engineering safety and quality, the foundation pit deformation monitoring is particularly important. The traditional deformation monitoring needs a lot of field works, and workers have to spend hours and hours outside on collecting the data. Close-range photogrammetry is a measuring technology which can determine the appearance, shape and geometric position of goal from close range. Using Close-range photogrammetry for the deformation monitoring of the foundation pit can overcome the shortcomings of traditional measurement, and can reduce the field works. The precision can also meet the need. Close-range photogrammetry improves work efficiency greatly, and then leads to the direct economic benefit.When using the Close-range photogrammetry for the deformation monitoring of the foundation pit, the first thing is non-metric camera calibration which solves the camera distortion parameters and inner orientation elements. Then laying out control points in the surveyed area, using the actual coordinates and the coordinates of the control points’ image points can solve the exterior orientation elements. Then we can determine the coordinates of each point in the photo. Compared the monitoring data with the previous monitoring data, we can get the deformation in all directions of the foundation pit.A new method using correlation coefficient that improves the traditional camera calibration method is proposed in this paper, we used the method to accomplish the experimental camera calibration, and determine the best scheme of the size and layout of the control points by the experiment. Appling the conclusion to the deformation monitoring of the foundation pit of TianZhu road station of Hefei rail transit line 2, the deformation data of the Close-range photogrammetry and the results of the traditional total station monitoring are basically the same. Using the close-range photogrammetry for the deformation monitoring of the foundation pit is feasible because it can meet the monitoring accuracy requirement, and achieve satisfactory results.