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strings and will then automatically obtain the proper stereoscopic
image of the total surface.
3. Outline of a proposed working procedure
3.1 Preparation of photographs and, their orientation in the plotter
The principal points are marked on each photograph and stereos-
copically transferred to the other one. A straight line, connecting
the two principal points on each photograph (photo base) is marked
on the edges of the photographs. Another straight line, perpendic
ular to the above mentioned base line and passing through a
point in the middle between the two principal points is marked on
the edges of each photograph as well.
Finally the photographs are placed on the table of the plotter in
such a way that the marks on the edges of the photograph coincide
with the fiducial lines marked on the table and fixed with the
metal frames.
3.2 Orientation of the surface for approximate compensation of errors
in absolute orientation and model deformation
The optical distance of the surface from the eyes Zin the
mean position (35.00 mm on the scale) equals 300 mm.
The height scale can therefore be determined by the formula:
c 300.0 mm (1)
2= h H0
where Sz height scale
h flying height above sea level
H0 mean height of model above sea level.
For H0 we can also take the mean of the given control heights.
Actually Ho should correspond to the mean of the heights of the
two principal points, and if available (through aerotriangulation)
these values should be used.
The desired Z-readings for given control points can then be found
by the formula
Z< 35.0 mm (Hi H0) Sz (2)
where Hi given height of control points above sea level.
With these data computed, the setting of the surface can be
computed by setting the Z-carriage on one of the computed values
Zj and correcting the surface with the help of the nearest situated
setting screw in such a way that the surface apparently intersects
the given point. This procedure is carried out in turn at all control
points and then repeated, until no further corrections are necessary.
