Target Free Distortion Measurement Using Close Range Photogrammetry

In this paper، an automatic close range photogrammetric method for deformation extraction from the object surface has presented. In opposite of the conventional close range photogrammetric approaches، here، utilizing targets is not mandatory. Indeed new feature extraction and matching algorithms can match corresponding image features with high precision in whole object surface. Therefore، the large number of matched points can remove the limitation of accuracy and network reliability in the case of using target for deformation extraction. After feature matching it could be used some linear computer vision and non-linear photogrammetry equations to solve the relative orientation and reach to model coordinate of check points. Then we use an initiative approach to match three-dimensional points of two epochs in the model space to determine the stable and unstable points and analyses the deformation of object. In this paper، after describing the automatic deformation extraction theory، the absolute deflection behavior of a foam beam under a pressure has been measured. To assess the accuracy of the proposed method، a comparison was made between this approach and the Australis software and the accuracy about 1. 5 mm was achieved. According to several tests performed using this technique، the accuracy of a few millimeters in some meters distance from an small size object is reachable.