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Targeted control points
Calibration grid points on picture-carrier plate
Figure 1. Changes of the picture-carrier coordinates. a) À test where the measurements were started immediately after the system
start-up. The light source was the stereoplotter's fluorescent tube. b) A test where special care was taken to reduce the variation of
temperature. The light source was placed outside the stereoplotter.
CONCLUSIONS
The experiences show that the photogrammetric system
calibration, which corresponds to the photogrammetric survey
process, can be used to establish the accuracy of the
coordinates of the measured terrain points. It has also been
possible to find out the critical parts of the process. They are
the resolving power of the camera/film combination, the image
deformations due to heat in the stereoplotter, the capabilities
of the stereo-operators, and the characteristics and
interpretability of the ground objects. Accordingly, corrective
measures can be taken to improve the mapping accuracy. They
are the training of stereo-operators, image motion
compensation, the careful handling of photographs throughout
the process, and the control of image deformations in the
stereoplotter. The research on the photogrammetric system
calibration has also influenced the instructions and
recommendations on photogrammetric surveying in Finland
(The Finnish Society of Photogrammetry and Remote Sensing,
1993 and 1995). In the future use of digital images will
improve the survey process, for example, in respect of image
deformations. As the calibrated stereomodel of Rusko is
available in digital form, it can be used for the system
calibration of applications of digital photogrammetry, too.
489
REFERENCES
Blachut, T.J., Chrzanowski, A. and Saastamoinen, J.H., 1979.
Urban Surveying and Mapping. Springer-Verlag, New York,
372 p.
The Finnish Society of Photogrammetry and Remote Sensing,
1993. Instructions for large-scale photogrammetric mapping.
Report 1/1993, Suomen kuntaliitto, Finland, 14 p. Available in
Finnish.
The Finnish Society of Photogrammetry and Remote Sensing,
1995. Recommended procedures for aerial photography.
Report 1/1995, Suomen Kuntaliitto, Finland, 17 p. Available in
Finnish.
Niskanen, J., 1990. Experimental work on large-scale
photogrammetric mapping in Kaukajárvi area. Report,
Tampere University of Technology, Geodesy and
Photogrammetry, Tampere, Finland, 26 p. Available in
Finnish.
Rantaniemi, H., 1993. Calibrated stereomodel of Rusko.
Report 1993/2, Tampere University of Technology, Geodesy
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996