Cl PA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
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Figure 4. Ground control unit with monitor in the centre,
remote controller on the right and battery for the monitor
downside of the monitor
Figure 3. Olympus Camedia C-4040
The video-out port of the camera was used to transmit the
cameras view to the ground. The normal PAL-signal was send
through a coaxial wire.
The wireless infrared control of the camera was rebuilt and the
IR LED was connected to a thin wire and fixed before the
Sensor at the Camera. IR signal only bridge short distance (max
10 m) and have problems in hot air conditions.
The calibration of the camera has been done by BAAP software
using the test field in ETH-Ziirich. 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 and focus length
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.
The balloon is approx. 2.5 m. in diameter and 8 m 3 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 m 3 He effect
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 3 ). 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.
Figure 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.
