30 
For the iterative adjustment of the Wild A7 strips on corner points, the reduction 
factor was only about 25% each four iterations. Here, 28 iterations were necessary 
and even then the largest change during the last four iterations was 0.43 m. 
This slower convergence may have been caused by the larger number of tie points 
used in each overlap, and the resultant smaller relative weights of the ground control 
points. Therefore, for the other adjustments of the Wild A7 strips the weights of the 
ground control points were increased to 10. These weights were also used for the 
adjustment of the Nistri TA3 strips. 
In addition, the first iterations of these adjustments were performed with pairs 
of overlapping strips as units, instead of with single strips. This proved to be a very 
effective way of speeding up the convergence. Besides, it has the advantage that one 
iteration for all strips requires only little more than half the time required for trans 
formation of all the strips individually. 
RESULTS OF THE TRIANGULATIONS AND ADJUSTMENTS 
a) Residual parallaxes 
Table II gives the root mean square value of the residual parallaxes, 
\vv~\ 
n 
obtained in the analytical triangulations of the eight west-east strips both for the 
points used for relative orientation and for all other points. The strips are numbered 
from north to south; the parallaxes have been reduced to the approximate photo 
scale 1:80 000. 
The residual parallaxes in the Nistri TA3 triangulations are about 50% larger 
than those in the Zeiss Jena triangulations. This may have been caused by several 
factors. 
First, on the right-hand plate carrier of the Zeiss Jena Stereocomparator paral 
laxes are measured, not coordinates. For this purpose, small lead-screws are used 
which can be very accurate. Then, both photographs can be moved as one unit. This 
makes it possible to eliminate //-parallaxes while observing not only individual points 
but also the area around it. Further, all Zeiss Jena measurements are the average 
of three pointings. These were mostly within 10 g of each other. 
TABLE II 
— MEAN SQUARE VALUES OF RESIDUAL 
PARALLAXES 
AT PHOTO 
SCALE 1:80 000, 
AND NUMBER 
OF POINTS 
Strip 
Zeiss Jena 
1818 
Nistri 
TA3 
orientation points 
other points 
orientation points 
other points 
1 
6.9 [i 
(309) 
11.1 p 
(75) 
9.8 [i 
(260) 
16,4 (JL 
(120) 
2 
6.3 
(284) 
10.5 
(98) 
9.5 
(230) 
15.7 
(99) 
3 
7.4 
(323) 
11.9 
(99) 
8.7 
(260) 
15.5 
(105) 
4 
6.2 
(293) 
9.9 
(91) 
11.6 
(230) 
17.2 
(95) 
5 
6.4 
(302) 
10.8 
(71) 
9.8 
(270) 
17.2 
(104) 
6 
6.5 
(310) 
9.4 
(96) 
10.6 
(260) 
18.2 
(170) 
7 
5.4 
(252) 
9.6 
(80) 
9.9 
(260) 
16.2 
(171) 
8 
4.9 
(255) 
8.9 
(94) 
8.7 
(270) 
15.8 
(157) 
In the Nistri Stereocomparator, on the other hand, coordinates are measured 
on all three plate carriers, only individual movements of the plate carriers are possible,