SINGLE IMAGE RESTITUTION USING CLOSE RANGE PHOTOGRAMMETRY

Abstract

Close Range Photogrammetry has been used for the documentation of architectural heritage since more than a century. The architectural Photogrammetry is successfully used to extract geometric information from wide number of photographs which are taken stereoscopically or which are convergent. But the problem of working with single image has diverted the attention of many photogrammetrists these days, as most of the times to document architectural heritage monuments, stereo images are either damaged or not available at all. To take new photographs the problem may be the monument itself is damaged. To reconstruct such monuments, the evidence may be a single photograph either taken by a tourist or is available from old literature, or even be downloaded from internet. The problem with such photographs is that no information is available about the camera. For photogrammetric reconstruction, camera parameters are necessary. Limited literature is available on methods of extracting information from single images which uses the geometrical constraints available from the object within the photograph. Graphical method is a simple technique used by architect for restitution from single images which uses the object geometry to extract camera information. In the present approach, a methodology is developed to restitute from single images through an analytical approach in digital environment with graphical method as background. A database is generated for various camera parameters and their corresponding data calculated using the object geometry. If the corresponding data is calculated directly from the image, then the camera parameters can be extracted using the graphs generated from the database. To ease this process, an ANN approach is also included in the methodology. The developed methodology is validated using two different cases of photography, one is personally taken with amateur digital camera and the other is downloaded from internet treating both the cases as unknown camera geometry. The methodology proved the effectiveness of Close Range Photogrammetric principles, particularly the graphical method in the restitution from single images. The user should have a quite knowledge of assuming the correct geometry of the object such as parallel lines and perpendicular lines. The methodology is also suitable where control points are unavailable or cannot be measured as the monument maybe already damaged.