Study On Geometry Correction Of Bird's-eye-photo For Traffic Accident Scene

With the high development of automobile industry and transportation, thenumber of vehicle increased rapidly in recent years. This status leaded to the ratioof vehicle and roadway maladjusted. Additionally, Road traffic accident occursfrequently because of the bad traffic management. Traffic accident analysis must bedealt with higher requirement to meet the person's legal consciousness that enhanceunceasingly. The perambulation and draft of accident scene are the basis ofapproving the accident process, and also they are the main evidence of judgingaccident responsibility. A kind of traffic accident mapping system that is appliedand efficient is a necessary instrument to acquire the accurate data of accidentscene. On basis of analyzing the documents such as the domestic and internationalrelevant measurement system of accident scene, the Computer aided imagehandling technology and the computer graphics etc., this paper put forwards amethod used for measuring accident scene and the method integratesbird's-eye-photo taking, computer aided image handling and computer drawingtechnology. Secondly, the paper given geometry correction model and developedcorresponding software. Finally, the paper carried out experiment to verify themodel and the software. The bird's-eye-photo geometry correction belongs to geometry operation ofimage handling technology. The image geometry operation is made up oftransformation of image space coordinate and determination of pixel value. Thelinear geometry transform model is the simplest. Based on the linear model, the 82摘 要process of camera imaging analyzed in details and mathematics model establishedfor bird's-eye-photo geometry correction. The mathematics model is followed as: ? = C1x + C2y + C3 ?? ?X C7x + C8y +1 (1) ?Y C4x + C5y + C6 ?? = C7x + C8y +1 WhereC1 ~C8 are Undetermined coefficients； x , y are the point's coordinatesof bird's-eye-photo ； and X , Y are the corresponding point's coordinates indestination image. The mathematics model is neither simple linear model nor binary polynomialmodel, but nonlinear binary polynomials model whose coefficients areundetermined. In the model, there are 8 coefficients needed to be determined. Ifthere are 4 or more reference points whose space position and image position havealready been acquired, the 8 coefficients can be determined by making use ofleast-square technique, and then the coordinate transform relation of space planeand image plane can be determined. According to the mathematic model, the coefficient determination is theprocess of solving the mathematic equation by making use of reference point'scoordinate. Therefore, the coordinate precision of reference point is important forsoftware correction result. For the reference point coordinate of accident scene, thepaper put forwards a method (called four point method) that can acquire pointcoordinate quickly. The method acquires the reference point's coordinate ofaccident scene by the distance between reference points. This method shortens thetime of acquiring reference point coordinate taken by traditional method, simplifiesthe process of distance measurement, and decreases the factors that lead to themeasurement error, so the method makes the error little as far as possible from thesource of reference point acquirement. For the reference point coordinate of image,two methods can be applied, one is manual method, and the other is auto method. 83吉林大学硕士学位论文The former can acquire coordinate required quickly by clicking mouse on computerscreen. It's very simple and practical for application. This method can adapt t...