Airborne Digital Sensors – a New Approach

Digital imagery from satellites or multispectral and hyperspectral scanners is well accepted. Tremendous challenges are inherent in the development of a digital sensor to acquire imagery suitable for both high precision photogrammetric mapping and image processing for interpretative purposes. The performance of the film aerial camera is almost impossible to reach with current digital technology. Joint development work by LH Systems and Deutsches Zentrum für Luftund Raumfahrt (German Aerospace Centre) has produced encouraging results using forward-, nadirand backward-looking linear arrays on the focal plane to provide panchromatic imagery and geometric information, supplemented by further arrays for multispectral data. The geometric characteristics of line scanner imagery necessitate line by line rectification for aircraft tilts and shifts. Satisfactory execution of this process depends on supplementary data from high performance, onboard GPS and inertial measurement systems. Similarly, high demands are placed on other sub-systems, such as the camera mount, lens, electronics and storage technology. The software to process imagery from the sensor must meet several particular requirements arising from the three-line principle. In addition to rectification for aircraft tilts and shifts, rectification for terrain characteristics is also required in order to generate colour and false colour composite images, since the various multispectral arrays are in different places on the focal plane. The special geometry also impacts triangulation. Thereafter, the imagery can be processed using existing software packages from both photogrammetry and remote sensing. The concept has been demonstrated in several successful test flights. The production model is scheduled for market introduction in mid-2000. The imagery from the new sensor will fulfil many market requirements between the highest resolution film imagery (<0.1 m) and high resolution space imagery (1-10 m). The sensor’s unique blend of multispectral information with high quality geometric information will give rise to numerous new applications.