SWDC-4 LARGE FORMAT DIGITAL AERIAL CAMERA SYSTEM

摘要

Digital aerial imaging becomes a hot topic since the ISPRS congress 2000 in Amsterdam. Now, there are approximately 120 high-end or "large format" systems available. However, the price of those cameras is high, and most of them have problems such as a large number of image pairs to handle and lower height accuracy as compared with traditional aerial cameras. Siwei Digital Camera-4 (SWDC-4) is a large format aerial camera developed by Beijing Geo-Vision Tech.Co.,Ltd. in 2006 for meeting the need of topographical mapping. SWDC-4 is composed of four non-metric unit cameras or camera heads. It is of following main characteristics: changeable lens, large field-of-view (71°/92°), large base-to-height ratio (0.58/0.82 at 60% overlap), and high height accuracy. The paper describes the SWDC-4 large format digital aerial camera system in details. After a brief description of the system constellation special attention is paid to some key techniques, i.e. (a) calibration of nonmetric CCD cameras, (b) correction and rectification of unit images (c) internal bundle adjustment, (d) generation of virtual image. The results of the test block in Beijing are presented. The relative height accuracy of both GPS-supported aerial triangulation and absolute orientation for single pair can reach 1/10000. The geometric accuracy of stereo mapping from the view of convergent photography is analysed in details. The high geometric accuracy achieved by SWDC-4 is mainly backdated to its large field-of-view and large base-to-height ratio, and the reliable measurability based on the high quality of digital image. The experimental result proved that SWDC-4 meets the accuracy request of stereo mapping.