Visualization Of Contours Based On Augmented Reality

Contour lines is a common method used in maps to simulate the surface morphology,which can be used as a reference for the location of other features.The traditional paper contour map have long been used as an effective auxiliary tool for cognizing geography environment because of its easy to carry,easy to use and good macroscopic.However,with the development of information technology,the defects of the paper contour map are increasingly prominent.The popularity of contour lines is affected because topographic "dimensionality reduction" causes cognitive decline and single expression.Augmented reality(AR)is a new branch of Virtual Reality(VR).It has advantages such as combination of virtuality and reality,strong expression,good interactivity,user-friendliness and it has been widely applied to monuments restoration,entertainment,medical science,military,education and many other fields.By introducing in AR technology and augmented display of contour lines in a user-friendly environment,it is helpful for users to fully understand and grasp the true meaning of contour lines and topographic features.It is vitally significant no matter in professional researches or public applications.In addition,the introduction of AR technology also provides a new visualization method for contour lines.In order to combine AR with display of contour lines and achieve popularization application,key problems as follows should be solved:the first is that the calibration method of most non-metric cameras has the problem of usability.Checkerboard calibration that is widely used is limited to inconvenient carrying and easy to be interfered,so a more simple and convenient method is needed.Second,problems like camera tracking failure and virtual object jitter are also common in camera posture tracking.These problems which influence visual effect need to be lessened or eliminated,thus providing users with a much better experience.Based on the theory and technology of AR and aimed at augmented display of contour lines in videos,this paper analyzed the features of contour lines and carried out further studies on the main problems mentioned above.The main research contents and achievements are as follows:1)A method of camera calibration based on A4 paperTraditional method of camera calibration is complex and needs some given control points or checkerboard patterns,which is inconvenient for public application.In this paper,a method for camera calibration based on ordinary A4 paper was proposed.By extracting four sides(two pairs of parallel lines)in the image of A4 paper,the vanishing points in two directions of the image plane can be calculated.Then intrinsic parameters of camera can be calculated according to the relationship of vanishing points and camera parameters.2)A method of stable camera posture tracking based on nature features of contour lines.Based on the analysis of image features of contour lines,this paper used ORB algorithm to extract nature features of contour lines and used random sampling consensus(RANSAC)algorithm to eliminate mismatching,thus lessening the phenomenon of camera tracking failure.Meanwhile,forward-backward matching algorithm was used to improve the efficiency of filtering.Besides,the rotation matrix and translation vector from 3D real space to 2D image space can be estimated according to the result of matching.Finally,the method smoothed the rotation matrix and translation vector to diminish jitter between two adjacent frames of virtual objects.3)A method of virtual-Actual fusion based on contour marking boardSupported by the key technologies mentioned above,this paper analyzed the rendering process of AR scenes and studied the relationship of real cameras and virtual cameras.By correcting the contour lines on the marking board and transforming them into contour line vectors,3D terrain can be restructured and fused with videos,which provides users with a better understanding and cognition of contour lines and features of contour lines in a user-friendly environment.The results of experiments verified the validity and reliability of this method.Contour lines in AR environment are more expressive and user-friendly.The method can be applied in the fields of education,tourism and so on,and the results also provide a useful reference for other related researches.