Tunnel Measurement Based On Digital Graphic Processing

The tunnel detection is very important in rail transport, but our existed detecting facilities are time-consuming, laborious and imprecise. It has largely restricted the development of our railway transport. Based on the search for massive domestic and foreign correlation data, this paper combines the increasing sensing, image processing and computer storage technology to research and develop the tunnel inspection car.The tunnel inspection car that this paper presents is a dynamic method that based on the way of"television camera". The tunnel inspection car uses many CCD cameras to real-time collect tunnel section information. The information would form the digital image that the computer is able to handle, after A/D conversion by video acquisition card. Before to do the correspondence between image file and calibration document, the digital image should first be pretreatment by smoothing filter, removing noise and extracting contour. After the correspondence, the conversion from image coordinate to spatial coordinate comes to be true. Then we can obtain the information of tunnel section, such as the overall height, the width of the tunnel at arbitrary height. At last, we could generate the smallest integrated tunnel section to provide a reliable basis for railway transportation.At the realization process of the tunnel inspection car, the video that the CCD camera collects will be saved as a real-time H.264 format. It is effectively reduce the volume of data. The true value diagrams are used to do the camera calibration. This method takes nonlinear distortion of the lens. Then effectively overcome the impact of lens distortion. And we use the least squares method for extracting profile of the tunnel to ensure the accuracy of data points selected. The ultimate results that use oscillating error compensation to correct which could eliminate the impact of the sway, make the accuracy to further improve.Currently, the tunnel inspection car in Shenyang Railway Bureau is testing completed and put into trial operation in Guangzhou Railway Bureau. After a lot of testing, it proved all targets were reached the demand of design, and had achieved good economic results.