lution 
ion or 
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ropes 
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| order 
The balloon is approx. 2.5 m. in diameter and 8 m! in volume. 
As an uplift gas, Helium (He) has been chosen because its non- 
dangerous properties. Such balloons are available at companies, 
which make professional outdoor advertisement. 8 n? He affect 
an uplift of 8 kg, so far the weight of all components had to be 
carefully balanced. Bigger balloons have bigger uplift, but they 
also need much more He. The chosen volume is just fine for 1 
big bottle of gas (has 9.1 m?). This enables to work 2-3 weeks 
with one filling. 
The camera platform was built in the workshop of GGS in 
Speyer. The digital camera was fixed at a axe, which itself was 
connected to a triangle frame, turn able around 2 axes so that 
the weight of the camera forced the platform, to support always 
a nadir view of the camera. To reduce the swinging of the 
platform, a smooth-compensator was built in. Phi and Omega 
values should be small with this construction, Kappa had to be 
influenced by the rotation of the balloon., 
The triangle frame of platform was fixed with 6 ropes below the 
balloon. To the ground it was fixed with 3 ropes, each with 50 
m length. One rope was used as carrier for a video and a 
remote-control wire. 
  
igure 2. The camera platform below the balloon with the 
balanced holder of the camera and the ropes 
For image acquisition, Olympus Camedia C-4040 has been 
selected (Figure 3). Nowadays it is very difficult to get high- 
resolution digital cameras with fixed focus lens. It was a must 
to use one of the extreme values, either the small angled or the 
wide angled setting of the lens. The Camedia is known for its 
good quality and sharpness of the images, resolution is just one 
aspect. 
   
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part BS. Istanbul 2004 
  
Figure 3. Olympus Camedia C-4040 
The calibration of the camera has been done by BAAP software 
using the test field in ETH-Zurich. Detailed information on 
calibration will be given in following chapters. 
2.2 Ground Control Unit 
Ground control unit has parts mentioned and explained below. 
- Monitor 
- Remote controller for shutter 
- . Control ropes 
A small portable TV with a video-in plug and battery power 
was used as a cheap monitor solution. A frame protected the 
screen against direct sunlight and the control worked fine 
(Figure 4). 
Other part of the ground control unit was the remote controller 
for shutter. Because of being out of covering distance of interior 
IR-LED (5 - 10 m.), remote control unit with a wire-output for 
an external IR-LED has been used (Figure 4). 
The last part of ground control unit was the ropes. Ropes, which 
are light in weight but strong in stability, are selected. 
   
Figure 4. Ground control unit with monitor in the centre, 
remote controller on the right and battery for the monitor 
downside of the monitor 
3. CAMERA CALIBRATION 
The Camedia has been calibrated in ETH-Zurich using the 
BAAP-software. Because of being a zoom-camera, its 
calibration has been done both for maximum wide and 
maximum narrow angles.