12.
The computer programs for the transformation should be so de-
signed that corrections for known and significant systematic
errors can be added to the model coordinates before the trans-
formations.
The transformation programs should also admit possibilities of
adjustment between connecting models to avoid elevation discre-
pancies in the profiles due to change of model.
Systematic errors of the height coordinates can, if they are not
observed and corrected for, cause essential errors in the cal-
culation of cut and fill and for the setting out of the road
body and óf the drainage system. Great attention must therefore
be paid to the possibilities of adding numerical corrections to
the model coordinates before the transformation into the ground
coordinate system. Experiences from practical work presented by
Ternryd in (26) show, that adding corrections to the model.z-
coordinate for the influence of radial camera distortion before
the transformation improves the quality significantly, provided
that the evaluation equipment is practically free from signifi-
cant geometrical errors and that the radial distortion of the
camera, photograph, is estimated under working conditions. For
the adjustment and calibration of photogrammetric evaluation
equipments reference is made to Kaasila, (16).
As the transformation of the model coordinates into the ground
System generally is made by electronic computation, adding nume-
rical corrections for known systematic errors, radial distortion,
does not introduce any problems.
The problems of the systematic errors were discussed by Funk,
(12) in 1959 when he presupposes that the longitudinal profile
of the road-centerline is measured terrestrially and the eleva-
tions fo the photogrammetrically measured transverse profiles
are then adjusted in relation to the longitudinal profile in
order to improve the geometrical quality. As this method in se-
veral cases can be timeconsuming and expensive it seems to be
more efficient to correct the photogrammetric data for systema-
tic errors instead of adjusting the transformed datas.
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1
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(€ 9
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