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These ground control points suffice to transform strips 1 and 8. For the position 
ing of strips 2 to 7 of the Zeiss Jena strips, estimated X- and F-coordinates of points 
at the beginning and end of each strip were used. For leveling in the strip direction, 
relative heights of points at the beginning and at the end of each strip were derived 
from the statoscope heights of the exposure stations. For lateral leveling, estimated 
heights of a river in the eastern part of the block were used. With a parallax bar, 
river heights near two ground control points in the north-east and south-east corners 
were derived from the known heights of these points. Further, assuming an approxi 
mately parabolic rate of change in the fall of the river, an estimate was made of its 
height at a number of points. 
This procedure proved to be rather laborious. Two or three transformations of 
each of the strips 2 to 7 were required in order to level the strips in strip direction 
and to compare the coordinates of tie points between each two strips. 
Consequently, a different procedure was used for strips 2 to 7 of the Nistri TA3 
and the Wild A7 triangulations. These strips were approximately positioned and 
leveled in the strip direction by means of coordinates of tie points obtained from 
previously transformed strips. 
In order to provide somewhat more data for lateral leveling of the strips, an 
additional river height near a ground control point in strip 5 was determined. Also, 
several points were measured along the edge of a reservoir in strip 7. Further, after 
an initial leveling, height differences of all tie points and ground control points in 
each overlap between two strips were plotted against their F-coordinates. Correlation 
between height differences and F-coordinates indicates a difference in lateral tilt. 
On the ground of this data, the conclusion was reached that the first estimates 
of river heights required corrections. The corrections were largest for strip 7, and 
amounted to 10 m/km. The corrected heights were used for lateral leveling of the 
Nistri TA3 strips and the Wild A7 strips. 
b) Block adjustment 
Several horizontal block adjustments using different selections of ground control 
points were performed with each of the three sets of triangulated strips. Each adjust 
ment consisted of transformation of the X- and F-coordinates of each strip by means 
of a number of either second-degree or third-degree conformal transformations. 
First a block was formed from the eight strips by transforming each strip in 
succession to the coordinate system of one of the strips. Here only the tie points in 
the overlap between strips were used for the computation of transformation formulas. 
Next, the resulting block was transformed as a unit to the X, Y coordinate system. 
For this, only the ground control points in the four corners were used. 
Finally, for the adjustments by means of second-degree conformal transformations, 
an iterative adjustment procedure was employed in which each strip was transformed 
in turn. For each iteration of a strip, the coordinates of given ground control points, 
if any, and the transformed coordinates of tie points in overlapping strips were used 
to compute the transformation formulas. The iterative adjustment was continued 
until convergence was practically reached. The sequence in which the strips are 
transformed, the number of transformations, the number of strips included in each 
transformation, the choice of ground control points and of tie points, and the weights 
of the ground control points are variables that were decided upon separately for each 
adjustment.