A A EN
fe iE
results were also compared with the predicted ones computed
with the UDECK earthquake simulation program. Three
diagrams were produced independently. They have been
scaled to the same time and displacement axes and are
presented in Figure 4.
Similar, or even better results are expected from the
calculations of the third experiment using the genlocked Beta
professional video cameras.
4. FUTURE OUTLOOK
It is expected that in the near future the above described
system will be enhanced with certain features and
improvements, which are considered as absolutely necessary.
Firstly a better determination of the targets will be introduced.
Given the limited resolutions of commercial video cameras,
special measuring techniques should be used to achieve better
accuracy. These techniques make use of a circular target
which shows up as a rotated ellipse on the digital image. Sub-
pixel edge measurements, determined via a single dimensional
edge locator based on moments, are used to fit a rotated
ellipse to the target (Cosandier et al., 1992). Software tools for
sub-pixel edge location are under development. Accuracy of
1/20th of a pixel and better is possible by using this method.
Presignalised targets should be automatically recognised,
detected and measured in a fully opereational system.
The algorithm used should further be developed, in order to
include determination of the reliability of the results. This would
mean introducing appropriate a priori weights for the various
parameters involved and calculation of the a posteriori ó, later.
Moreover a high definition frame grabber should be available,
in order to prevent eventual loss of qualitative and quantitative
information during the digitization of the images.
The use of a graphics co-processor will enable the processing
of more frame pairs per second, thus achieving smoother 3-D
animation of the stereoscopic video.
Finally a friendly user interface should be developed to make
the system amiable by non-photogrammetrists, in order for
them to perform the appropriate measurements.
Furthermore, the system may later be integrated with a
dedicated data acquisition system consisting of two
synchronised high definition camcorders with known geometric
and radiometric characteristics. The use of digital video is also
an option under consideration, given the rapid development of
similar commercial systems.
Application fields of the system developed are mainly industrial
mensuration problems such as quality control cases, crash
tests or even military implementations. Further possibilities
may include kinematic studies in the field of biostereometrics.
5. REFERENCES
1. R. Akka, 1991a. Software Concepts for Stereoscopic 3D
Graphics. StereoGraphics Corporation.
2. R. Akka, 1991b. Automatic software control of display
parameters for stereoscopic graphics images. StereoGraphics
Corporation
3. Bayer, H., Kersten, T., Streilein, A., 1992. Metric accuracy
performance of solid-state camera systems. Videometrics I,
SPIE vol. 1820, Mass. 1992, pp. 103-110.
4. Cosandier, D., Chapman, M.A., 1992. High precision target
location for industrial metrology. Videometrics II, SPIE vol.
1820, Mass. 1992, pp. 111-122.
5. Chen, C., Scarpace F. L., 1990. One Dimensional Search
for Digital Matching. International Archives of Photogrammetry
and remote Sensing, Vol.28, Part 3/2. Commission lll
Symposium, Wuhan.
6. Gerorgopoulos, A., Tournas, E., Mouzakis, H.P.,
Vougioukas, E., Carydis, P. 1995. Determination of Seismic
movements of monuments using stereoscopic video. Optical
3-D Measurement Techniques Ill, Vienna October 1995,
pp.454-462
7. J. Gradecki, 1994. The Virtual Reality Constraction Kit. John
Wiley & Sons, Inc.
8. He, G., Novak, K., Feng, W., 1992. Stereo camera system
calibration with relative orientation constants. Videometrics ll,
SPIE vol. 1820, Mass. 1992, pp.2-8.
9. R. Jain, R. Kasturi, B. G. Schunck, 1995. Machine vision.
McGraw-Hill
10. L. Lipton, 1991. The CrystalEyes handbook. StereoGraphics
Corporation, 1991
11. Snow, W. L., Childers, B.A., Jones, S.B., 1992. Recent
experiences with implementing a video based six degree of
freedom measurement system for airplane models in a 20 ft
diameter vertical spin tunnel. Videometrics Il, SPIE vol. 1820,
Mass. 1992, pp. 158-180.
12. D. Vernon, 1991. Machine vision. Prentice Hall International
(UK) Ltd.
ACKNOWLEDGEMENTS
The assistance and contribution of the members of the
Laboratory of Earthquake Engineering of NTUA and of MEGA
Channel to this study are gratefully acknowledged.
116
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996
KE
AB
Thi
(AN
exp
exti
a le
ac
real
KU
Die
kün
und
eine
Kla
dur
Sin
Art
ver:
Suc
clas
199
199
stat
Am
met
kno
abil
trai
to g
kno
Th
refe
slow
alg
the
al.
al. |
