The Application Of Digital Close-range Photogr Ammetry In Bridge Deformation Measurement

Digital Close-range Photogrammetry is such a technology that to get the size and motions of the objects by using photography and image processing. All can be photographied are the objects of Digital Close-range Photogrammetry, in order to get 3d coordinates of point cluster on the objects and length, area and bulk of the object in the 3d frame of axes. Digital Close-range Photogrammetry is non-contact measurement method,it will not damage the target and have a high information capacity,the message can be easily stored and be reused,it has a high accuracy ,high speed.This technique is especially suitable for measuring the objects containing large points or those located at dangerous position.Digital camera,as a photographic device of Digital Close-range Photogrammetry, with its low prices, mature technology ,has been applied more and more. Using digital cameras as the equipment for photography also attracted more and more concern and research of scholars in many fields . This paper studies on the basis theory and method of realizing three-dimensional measurement based on uncalibrate digital camera, and applies the results to the deformation measurement of bridge structure.The contents of this paper are given as follows:first this paper gives the basic theory of Digital Close-range Photogrammetry .Then digital imaging geometric model of camera are analysised and the suitable method for the camera calibration are choosen in order to get the interior position elements and the optical lens distortion coefficient of the camera.It is inevitable to lay out the artificial marking signs to identify the object when photographing images using digital camera. Based on the study of sharp and layout of artificial marks, combining actual environment of the experiment, suitable artificial marks are selected. After collecting the image of actual object based on the principle of image collection, data processing can be done. Using professional modeling and measuring software PhotoModeler Pro 5 as the tool of image processing, the characteristics dots and lines are identified, then homologous points should be matched,next actual three-dimensional coordinates must be introduced into the software,this is very important stage. Finally,coordinate three-dimensional coordinates of feature points can be measure , but also three-dimensional model of bridge be built, and its surface texture are given. The paper finished by summarizing the total word has been done and concluding the results. Further research work is also presented.