Development of digital aerial cameras

Abstract

Digital aerial cameras have replaced analogue aerial cameras in several countries. The development for operational aerial photogrammetry started with the line scan camera ADS40, followed by Z/I Imaging DMC and Vexcel Imaging UltraCam. Recently the line scan camera Jena Optronik JAS-150 was introduced. The capacity of the UltraCam was enlarged by replacing the used CCDs with 9μm pixels over 7.2μm to 6μm for the UltraCamXp, having 196 Mpix. The DMC and the UltraCam are system cameras, reaching the large number of pixels by a combination of 4, respectively 9 CCDs. Even if the large format line scan cameras have demonstrated their geometric potential, the major replacement of analogue cameras came by the digital large frame cameras, while the line scan cameras found their major field with orthoimages. In the meantime digital mid-format cameras, equipped with a single CCD-array, with approximately 39 Mpix took also a share by the replacement of the analogue aerial cameras. Their combination with GPS and inertial measurement units (IMU) compensates partially the disadvantage of handling a high number of images. The mid-format cameras are equipped with Bayer pattern, limited to 3 spectral bands opposite to the 4 spectral bands offered by the large format frame and line scan cameras. This changed by the introduction of mid-format system cameras RMK D from Z/I Imaging and UltraCamL from Vexcel Imaging. In addition now camera systems equipped with 4 mid-format cameras as the IGI Quattro DigiCAM and the Trimble Aerial Camera (TAC) (former Rolleimetric) AIC-x4 are available. These cameras are not offering homogenous virtual images as the DMC and UltraCam. Just recently a new situation came with the development of large format monolithic CCDs by DALSA. Based on this Z/I Imaging introduced now the DMC II 140, having 11712 × 11200 pixels on one CCD with 2 sec frame rate. In the fall the DMC II 230 (230 Mpix) and in the spring 2011 the DMC II 250 with 17216 × 14656 pixels with 1.7 sec frame rate will follow. This corresponds to the dream of photogrammetrists replacing the film just by one CCD. The geometric performance of the large format digital cameras and the mid-format camera TAC and Quattro DigiCAM have been analyzed in a test of the German Society of Photogrammetry and Remote Sensing (DGPF), showing an advantage of the large format digital cameras against scanned analog photos. The monolithic DMC II 140 was analyzed separately, demonstrating an excellent geometric performance better as other cameras before.