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of 3000 m, the ground sample distance is 16 cm with a total swath width of 3,75 km. Because of the high data rate 
during flight the airborne camera system is available with an in-flight storage capacity of between 200 and 500 GByte. 
The camera has temperature stabilization and compensation for the CCD lines. In addition special care has been taken 
to avoid condensation on critical components. 
Figure 3 illustrates schematically the direct digital workflow of ADS in comparison to the film based workflow. 
4 LINE SCANNER IMAGE PROCESSING 
The push-broom type of this geometric CCD line configuration simultaneously acquires the multispectral and 
panchromatic images by a high frequency sampling of the different sensor lines. As already mentioned, the raw images 
contain distortions due to roll, pitch and yaw movements of the aircraft. Figure 4 shows this effect and its correction on 
a flight over Berlin. The top image is raw. The bottom image has been rectified and looks like a conventional aerial 
‘photo. Note the correspondence between the edges of the rectified image and the roll of the aircraft. Tilts have been 
compensated by adjusting each individual CCD line image for the attitude of the aircraft, using Global Positioning 
System (GPS) and Inertial Measurement Unit (IMU) data. These have been collected during the flight and been written 
together, with the acquired image data, into a Mass Memory System (MMS). A synchronized clock times the events of 
IMU, GPS and sensor line recording in order to achieve a high quality imagery, in particular in the case of stereo 
images (Tempelmann2000). After the flight a ground processing system archives all the data, followed by post 
processing to convert the data into different levels of image products (image rectification, Digital Terrain Model 
(DTM), orthophoto, mosaic production, etc.). 
5 APPLICATION POTENTIAL 
Provided that the new digital airborne camera system fulfills all the listed requirements, it will certainly revolutionize 
photogrammetry and remote sensing in quality and fast availability of the data. In principle the image data can be 
transferred from the aircraft directly to the user’s ground-/workstation. In particular the simultaneous imagery with 
many spectral bands, including two NIR channels definitely has a strong advantage over the film camera. But for the 
highest spatial resolution with ground pixel sizes of 50 mm and below the film camera will still be the instrument of 
choice. 
The very large swath width combined with a high spatial resolution and multispectral channels makes ADS very cost 
and time effective which can be demonstrated by the following examples: 
e Greater San Diego, with an area of about 500 km”, could be 3-dimensionally mapped with a resolution of 25 cm 
within a one hour flight time producing a panchromatic data volume of about 120 Gbyte. 
+ To map the Ohio river with the same ground resolution and a swath width of 5 km it would take about 5 hours with 
a data volume of about 500 Gbyte, which still fits the storage capacity. 
For several remote sensing tasks with multispectral applications the large field of view (FOV) perpendicular to the 
flight direction requires a correction of the data with respect to the viewing angles. A Bi-directional Reflectance 
Distribution Function (BRDF) catalogue for many typical land/vegetation surfaces will be available (Demircan2000). 
Using the new generation digital airborne camera aerosense companies will not only increase their annual acquired data 
volume by orders of magnitude but also the simultaneous acquired multichannel data will provide all kinds of 
applications illustrated in Figure 1 and 2. The combination of high resolution stereo images with 5 different wavelength 
channels in the VIS to NIR range having mathematically well known filter curves will certainly offer new airborne 
remote sensing applications. Because of the absolute calibration for the sensor system atmospheric corrections are 
possible which enable measurements of time-varying parameters even when these are small. In addition data fusion 
with satellite data will be very effective and will therefore improve the quality of the data products for the customers. 
Figure 5 demonstrates that many of the applications in forestry, urban areas, water control, agriculture and vegetation 
can be covered in terms of swath width and spatial resolution on the ground because of the optical and geometrical 
parameters of ADS. Figure 6 shows the ground sample distance as a function of flight altitude for the staggered 2 x 
12000 CCD array. The ADS performance is characterized by the focal length of 62.5 mm. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 255