Photogrammetric Processing of Low Altitude Image Sequences by Unmanned Airship

Low altitude aerial image sequences have the advantages of high overlap, multi viewing and very high ground resolution. These kinds of images can be used in various applications that need high precision or fine texture. This paper mainly focuses on the photogrammetric processing of low altitude image sequences acquired by unmanned airship, which automatically flies according to the predefined flight routes under the controlment of autopilot system. The overlap and relative rotation parameters between two adjacent images are estimated by matching two images as a whole and then precisely determined by pyramid based image matching and relative orientation. The matched image points and ground control points are then used for aerial triangulation with collinearity equations. The aerial triangulated high resolution images can be used to obtain precise spatial information products, such as Digital Surface Model (DSM), Digital Ortho Map (DOM) large scale Digital Linear Graphic (DLG) and three-dimensional (3D) city model. Experimental results show that the developed remote sensing system is qualified for high overlap and high resolution stereo imagery acquisition. Moreover, the proposed approaches are effective for photogrammetric processing of low altitude image sequences, and have well potentials in large scale topographic mapping and precise 3D reconstruction areas.