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Title
Proceedings of the Symposium on Progress in Data Processing and Analysis

4.4. Object tracking
Two different projects indicate the potential of
CCD camera based methods for object tracking.
For the determination of 3-D velocity fields in
turbulent flow a three CCD camera arrangement
was used to record laser sheet illuminated particles
in a laboratory water channel (Papantoniou, Maas,
1990). The technique is fully automatic, uses a
multimedia photogrammetric approach and can
track the particles with high spatial precision and
reliability, and very good temporal and spatial
resolution. About 700 particles can be positioned
and tracked over as many as 350 video cycles with
a tested accuracy of [i x y = 0.04mm and fi z =
0.04mm in an object space volume of 150 x 150 x
18 mm 3 .
from comparison with the true value of the distance
from 93 ruler positions.
5. Conclusions
It is our experience that the modular concept of a
workstation-based digital photogrammetric station
is a very appropriate and useful approach for a
research and development group. The fast progress
in the development of general computer
components on the hardware and software side
allows for permanent and timely upgrading of the
system. So far we have not encountered any
problem with upward-compatibility. As an
example, the transfer of our C software packages
from Sun-3 (Motorola MC68020 processor) to Sun
Figure 9: Biomechanical application. Trajectories of markers overlaid onto a sequence of CCD frames of
a walking person.
Related to biomechanical applications a person was
marked with retro-reflective targets. Thus walking
through our large testfield the trajectories of these
markers were determined by three CCD cameras,
the frames of which were acquired simultaneously
and recorded on video tapes. Figure 9 shows the
trajectories overlaid onto a sequence of images.
Problems of occluded and only partially imaged
targets deserved special consideration. The person
was carrying a 50 cm long ruler with one marker at
each end. An RMS error of 1.7 mm was achieved
SPARCstation (SPARC RISC processor)
technology needed only recompilation. Our
independence of any special equipment
manufacturers and the use of many hardware and
software standards guarantees for fast and
uncomplicated further development of our system’s
components and for easy integration of new
algorithms and procedures. Other important factors
are the ease of access to third party hard- and
software and the compatibility with external groups
and systems.