nsiderable 
ie Z-coor- 
map than 
ct that in 
ng district 
ed. 
mplemen- 
ig costs. 
educed to 
fact that 
on of the 
ontrol net 
the trian- 
base is set 
Is is done 
a known 
ing in the 
tween the 
ion points 
definable 
1e coordi- 
the fitting 
ormations. 
] to make 
? does not 
toring the 
that it is 
ig sharply 
ts as thin 
he stereo- 
vhere the 
ed on the 
instruments 
e elevation 
constructed 
ferences in 
victure, the 
  
  
cross. This method guarantees the highest accuracy when transferring scale as well 
as azimuth between models in terrain lacking details. In the archipelago the cross 
is placed if necessary on the water surface, and the measuring mark is stereo- 
scopically adjusted on the nearest shore line before the planimetric adjustment. 
The cross points must be placed as accurately as possible on the side-lines of 
the model, because the accuracy of the surveying of the model is less high in the 
area outside these lines (cp. Hallert [5]). 
To increase the accuracy of the triangulation, more than two connection 
  
  
  
  
points may be marked out 
on the negative. Besides the 
side points, one or more 
points may thus be placed 
near the principal point of 
each picture, where the 
model errors, caused by 
defects in the reciprocal 
orientation are small. The 
central gravity of the cen- 
tral cross points are con- 
veniently used as rotation 
centre at the transference 
(fig. 3, points 01°, 12°, 23° 
etc.) cp. Hallert. 
11.3. Elimination of the 
effect of the systematic in- 
strument errors. 
The other primary 
problem is the systematic 
planimetrical deformation 
of the stereoscopic model, 
"which depends on defects 
of the photographs and 
stereo instruments. 
Influence of the systematic instrument error on the shape of the triangulation 
strip can be eliminated by turning every other model in the strip 200° in relation 
to the other models at the plotting in a stereoinstrument. Fig. 1 shows the aspect 
of the strip after this operation and as a comparison the aspect of the strip when 
connecting the models without turning them. It is here presumed that the plani- 
metric deformation of the model is exclusively caused by errors in the plotting 
instrument. 
Thanks to the method described under point II.2, the connection points can 
be given regular positions, independently of the aspect of the terrain surface, 
which increases the probability of eliminating the systematic model deformations 
by turning the models.