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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