CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
Figure 2. The camera and its special-designed platform
Figure 4. Balloon during flight campaign
For all the theater, 214 aerial and 275 terrestrial photos are
taken. Aerial photos have been used for mapping the plan where
terrestrial photos for evaluation of facades.
On the aerial photos, ground control points are clearly visible.
This was the result of painting them blue, so that the effect of
reflectance had been minimized (Figure 5). On terrestrial
photos, there wasn’t a reflectance of control points, because
onto them as a measure marks. 80 ground control points were
used for all the theater. (Figure 1)
Another type of control points was defined for the terrestrial
photogrammetry for facades. Comers of stone blocks have been
chosen for this purpose.
All of them have been measured by terrestrial methods with a
total station Pentax ATS 102.
Figure 1. Layout view and control points
2.3 Image Acquisition
Aerial images have been acquired from a helium balloon with
an Olympus C-4040. Balloon was 2.5 m in diameter and has a
volume of approx.8 m 3 . It can lift up to 8 kg, so the
optimisation of platform and the camera on the balloon has a
big importance about the weight of them. The camera and
platform have been selected and built so that their weight will
be minimum. Even the ropes have been selected so that they
would be strong enough for this balloon and minimum in
weight.
The balloon carries an aluminium frame as a camera platform
and this platform is hanged downside of the balloon using 6
ropes. 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 the 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 (Figure 2). 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.
To the ground the balloon was fixed with 3 ropes, each with
50m length. One rope was used as carrier for a video and a
remote-control wire.
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. 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 3).
Figure 3. Ground control unit with monitor and remote control
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. Both worked
fine even with 50 m wired connection, video control and the
remote control of the camera. Also the sharpness of an image
has been visible when the image was frozen for a few seconds
when the camera had shot the photo.
