Fig.4 Program steps
Since the control-points are not in a numerical form, they first have to
be digitized. This is done on the drawing table of the instrument. The
points are stored for further use, so this step is omitted in subsequent
revision cycles.
Depending on the requirements, up to a maximum of 8 control-points can
be introduced. Planimetric, height and full control-points (planimetry
and height) are acceptable. In addition, the operator can introduce up
to a maximum of 20 points for the relative orientation if needed.
Normally 3 iterations are sufficient for the calculation. From
experience, the time required for the separate steps on the average:
digitization of control-points
measuring points on instrument
calculation
setting the values, control
25 min.
15 min.
3-10 min.
10 min.
These values are certainly not definite and can probably be reduced. In
any case we have been able to save 10-20 min. per model.
3.4 Program tests
Following the usual functional tests with simulated data, the program
was tested in a first phase with regard to accuracy and stability using
various control-point configurations. Aerial photographs were taken of
a region typical for Switzerland (hilly to mountainous). The signalized
points were all geodetically determined points with an average RMSE of
+5 cm in planimetry and height.
From this test material, a total of 30 models with a variety of control-
point configurations were oriented and tested. The results were good for
all of the models. After introducing the orientation settings in the
instrument, the models were always free of parallax. The accuracy of
the fit in planimetry was 0.05-0.15 mm and in height 0.5-1.0 m.