Hyper resolution image mosaics with unbounded vertical field of view

摘要

This paper presents the framework for the creation of hyper resolution image mosaics (HRIM) with a full horizontal and unbounded vertical field of view. Additionally, the hyper-resolution images are mapped to a format compatible with a geo referencing frame. In this manner the images can be viewed using standard mapping services. The measurement device consists of eight cameras covering the full 360 degree horizontal field. The unlimited vertical field of view is obtained by moving the device, e.g., by sinking it down a mine shaft. The cameras are synchronized so that with each frame the full horizontal field of view is captured. The camera sensors are calibrated to an onboard inertial measurement unit (IMU) which allows the reconstruction of the position of each sensor in a world coordinate frame for each captured image using rigid transformations. Perspective projection onto an open manifold (cylinder) allows for the integration of all images into an HRIM. Constrained tensor-polynomial approximations are used to obtain geometric maps, i.e., a distortion lattice, from the image coordinate system onto an open cylindrical manifold. From this lattice binary masks are derived for each projected image. A multi band blending algorithm is implemented for the final composition. The HRIM are then tiled and stored on a GIS mapping server from where the HRIM can be viewed on any device running an HTML browser. It should be noted that this approach provides a significant advantage since viewing the large HRIM is not computationally intensive and can even be done on tablets. The framework has been applied to the remote inspection of deep vertical shafts. (C) 2020 The Authors. Published by Elsevier B.V.