On the accuracy potential of large format solid state matrix sensor cameras onboard an aircraft

The continuing progress in the resolution and quality of solid state matrix sensors has made the use of digital cameras onboard an aircraft an interesting option. Although by far not yet comparable to the resolution of scanned 9” x 9” film, direct digital data capture is meanwhile a viable alternative for a number of applications. Direct digital data capture avoids time consuming development and scanning processes and does yield a potential for online or even realtime data processing. While first realizations of digital cameras onboard an aircraft were based on linear array sensors used in a pushbroom principle, area sensors with resolutions of up to 4090x4096 pixels being commercially available today are gaining importance. This paper presents four practical studies on the helicopter-based use of high resolution digital stillvideo cameras for aerotriangulation and the automatic generation of digital elevation models and orthophotos. Test regions include mountain areas, an alpine village, the bottom of a shallow lake and a landslide area in Switzerland. The current performance and future developments of solid state matrix sensors are shown, and the advantages and disadvantages of the use of digital cameras in aerial applications are discussed. Using self-calibration bundle adjustment techniques, externally verified accuracies of 2cm for planimetry coordinates and 5cm for height coordinates were obtained in digital aerotriangulation using imagery of 1 : 18’000 scale; using 1 : 64’000 small scale digital imagery over an area of 3.6 x 2.4 km2, a checkpoint RMS of 9cm for planimetry coordinates and 25cm for height coordinates was obtained. In the generation of digital elevation models by multi image feature based matching, a precision of 0.03% of the flying height above ground could be achieved.