426
the reference values which in this case were obtained by the procedure
in the autograph A8 must also be known. The accuracy of the auto
graph values depends on several different factors among which are
the interior orientation of photographs, the relative and absolute
orientation of the model and the accuracy of the stereo-plotting machine
the most remarkable. There is no information about the accuracy of
the interior orientation, therefore such data must be estimated. The
standard error of unit weight of the image coordinates is supposedly
0.010 mm for a radius of 150 mm (19). In order to get an idea of the
irregular errors in the image coordinates which are caused by film
shrinkage, an adjustment of the measurements of the fiducial marks
has been performed. Five parameters, namely two translations, one
rotation, and two scale factors have been used in adjusting the discre
pancies between the measured and the given values. The root mean
square value of all the determinations of the standard errors of unit
weights was 0.020 mm. According to the performed test measurements
of the grid method the autograph A8 had a standard error of unit
weight of 0.005 mm in the projector SGale. The regular errors of the
instrument were all through smaller than their standard errors and
have therefore been neglected in the computations. The standard error
of unit weight of the relative orientation was determined by y-parallax
measurements at 15 points. The following results are found:
Strip 6010a M = 0.008 mm
„ 6010b M = 0.010 „
„ 6011 M = 0.006 „
where M = the root mean square value of the standard errors of unit
weights.
M obtained by the parallax measurements has also been used in
determining the accuracy of the absolute orientation.
Fig 3. Locations and notations of
elevation control points.