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International cooperation and technology transfer
Mussio, Luigi

Table 3: Relative position errors of backprojected
control points in reference system S c .
rad + dec
rad-r ihm
rad2 + dec t- thin
mean Xc
mean Y c
std Xc
std Y c
As pointed out in tables 2 and 3, beside of performing a
calibration with less or more distortion parameters, one
should choose the camera mode! according to lower
backprojection errors, which are represented by (mean
Xw, meanY w ) and (std X w , std Y w ) or, equivalently, by
corresponding relative values computed in I c . while
(stdr, stdc) can give a feeling of superimposed noise.
Today, the camera calibration is becoming even more
an important issue in the digital photogrammetry field,
in the same time non-metric photocameras are widely
spreading on the market, due their relative low price
and improvement of image quality, that is sufficient for
image processing. In order to put in touch these two
fields, in the ambit of the Photogrammetry course we
have developed an alternative calibration method, in
which the Tsai-Lenz and Cohen-Hemiou algorithms
were properly revised. The procedure was then imple
mented as teaching software, in which a graphic inter
face helps the user for data input, evaluation of calibra
tion parameters results and assessement of Its accuracy.
The proposed algorithm is able to taken into account
various combinations of lens distortions, allowing the
user to choose the best distortion model according to
the application field and calibration requirements.
Fig. 5 : DATA window for calibration parameters input
This work was developed with the project “Digital
surface modeling by laser scanning and GPS for 3D
city models and digital orthophotos”. partly financed
by MURST (Italian Ministry- of University and
Research) in 1998 as a project of relevant national
interest. National coordinator: Riccardo Galetto, Head
of the research unit Antonio Vettore.
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[5] Weng J., Cohen P., Hemiou M., October 1992.
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accuracy evaluation”, IEEE Transaction on PA ML
vol 14, n° 10, pp965-980.
Fig. 6 : The PARAMETERS window showing the
calibration results.