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Proceedings of the Symposium on Progress in Data Processing and Analysis

concern aspects of the hardware - all calibration
procedures on the S9AP already run
automatically. This concerns more the quality
control aspects of obtaining good points.
Two methodologies used in this investigation
would be difficult to implement in an automated
system: adjustment of the video digitisation gain
and offset, and the selection of best matching
The former may always be a problem, due mainly
to the density range in aerial photography.
However in this case it was necessary due mainly
to the poor contrast exhibited by many of the
signalised points used. In a semi-automatic
procedure the points to be matched will in general
be natural tie-points instead of signalised points.
Images in the appropriate positions in the model
can be acquired (eg at the von Gruber points) and
the tie-points selected automatically based on what
image signal there is. The Digital Comparator
Correlator System (DCCS) from Helava Associates
Inc employs techniques along these lines in its
procedures for semi-automatic triangulation
(Helava, 1988).
The need to select best matching parameters was
also a direct consequence of the signalisation -
badly defined points are difficult to match with
template matching. This would also to some extent
be relieved by the use of natural tie-points: in
general, good signal content equates to suitability
for matching. If a constant parameter set is used, it
may be easier to pick out any failures that do occur,
whereupon alternative points could then be
selected on-line. It may still be necessary to match
signalised points, in which case a higher quality
signalisation is required, or the development of
supporting or alternative matching methods.
5. Concluding Remarks
The primary aim of the investigation was to use the
results of the bundle adjustments as a means to test
the quality of the calibration procedures developed
for the CCD cameras on the S9AP. The accuracy
level achieved with the digital measurements was
slightly lower than that for the manual
measurements. With the test data used, it is
difficult to separate out the exact source of this loss
of accuracy: some certainly lies in the image
matching techniques used, whilst small instabilities
in the calibration may have contributed also. The
conclusion for the calibration is that it is at an
adequate level for the actual purpose for which it
has been developed - DTM generation by image
The secondary aim was an investigation of aerial
triangulation with point determination by image
matching. The accuracy level is comparable with
manual observations, but a more thorough
investigation is required to determine the influence
of poor matching on the result. Aspects of semi
automation of the procedure have been addressed,
where the use of natural tie-points would provide
some additional advantages. If signalised points
are used, their imaging quality must be high.
6. References
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Precision Aerial Triangulation with Point
Transfer by Digital Image Correlation.
International Archives of Photogrammetry and
Remote Sensing, 26(3/1): 18-27.
BALTSAVIAS, E.P., 1988. Hierarchical Multiphoto
Matching and DTM Generation. International
Archives of Photo grammetry and Remote
Sensing, 27(B 1 l/III): 476-487.
BETHEL, J., 1986. The DSR11 Image Correlator.
Proc. ASPRS Annual Convention (Washington
DC), (4): 44-49.
DAHLER, J., 1987. Problems in Digital Image
Acquisition with CCD Cameras. Proc. ISPRS
Inter-Commission Conference on Fast
Processing of Photo gramme trie Data (Interlaken,
}j S c
Switzerland), pp 48-59.
1 he
GRÜN, A.W., and BALTSAVIAS, E.P., 1988.
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r 0 i:
GRÜN, A.W., and RUNGE, A., 1987. Projekt
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GÜLCH, E., 1984. Geometrie Calibration of Two
CCD Cameras used for Digital Image Correlation
on the Planicomp C 100. International Archives
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Helava, U., 1988. Digital Comparator Correlator
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PERTL, A., 1984. Digital Image Correlation with
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1987. The New Wild System-9 Analytical
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