The Research On Recognition And Detection Of Encoded Targets In Digital Close-rang Industrial Photogrammetry

Digital close-range industrial photogrammetry is a kind of measurement method thatmakes use of more photos taken from different direction and the principle of multi-view3D reconstruction. This measurement method has an extremely broad application prospectsin many fields. Usually the measuring system needs to paste up encoded targets and circletargets on the surface of object regularly and then solve the coordinates of two kinds oftargets precisely. When processing images and getting the coordinates of targets, encodedtargets play an important roles. In addition to containing the coordinate information, thecoordinate information of un-encoded targets is gotten by analyzing the positionalrelationship with special encoded targets. So precise recognition and accurate location inindustry are always research focus. We propose a set of coded design, detection,recognition and decoding algorithm theory and verify the theory, details are as follows.Firstly, this paper introduces several kinds of encoded target, analysis every kind ofencoded target advantages and disadvantages, draw up the principle of design of encodedtarget in big scene measurement and choose the best in our subject.Secondly, this paper discourses the process of dealing with encoded target, imagebinary conversion and the Canny edge detection is used to pre-process the image.According to deleting straight line, length criteria, shape criteria and embedding criteria,delete impurities graphics. Then use the modification of ellipse to obtain the coordinates oftargets precisely.Thirdly, according to modification of parameters of candidate ellipse, construction ofembedded ellipse, coordinate conversion, we can decode the encoded targets. For optimalinitial points of decoding, this method has no influence on the efficiency and improves theaccuracy of decoding.Finally, combining with these above-mentioned theories and with the help of functionof Matlab, recognition program is edited, according to three kind of images of targets, wecan analyze the encoded targets’ recognition results and recognition rate. The theory is testthat they have feasibility and practical value.