A Low-Cost Method and Surveying of the Historical Structures from Digital Resources

Abstract

A new method using optics in non-contact photogrammetry to find the dimensions of target objects by digital archive and/or open source digital images has been presented in this paper. In the proposed method, a reference object of known dimension must be present in the field of view of a pair of images collected at any two unknown arbitrary positions along the axis of camera (z-axis) and 2D size measurement (x-y) of other target objects, and it is done successfully with the help of the proposed algorithm. The presented method is applicable to the number of images(>=2) containing the target objects and reference object which are not in the same plane and which may be shot from any camera not known to the user. Hence, the internal and external specifications of the camera are completely unknown to the user. The method has been verified successfully to show its applicability in low-cost surveys by determining the dimensions of the Washington-Monument, Christ the Redeemer (Rio de Janeiro) and the Eiffel Tower (Paris) from open source images. Further, an example case of Notre-Dame Cathedral is demonstrated to find the size of the destroyed spire from the undestroyed reference structure. The results are being compared with known standard values of structures and the relative error percentage for all the cases using the proposed algorithm and are found to be less than 1%. The method may find applications in survey or analysis by old digital video footage or images from archive/libraries where the camera specifications are not known to the user.