Now, by applying an S-transformation on those four unit vectors to the
S-base of points ! and 2, one obtains the four c-vectors, which can be
used, when calculating the boundary values of the x- and y-coordinates
of those points, when acting as base-points.
Furthermore Baarda [1] and Van Mierlo [4] showed that the S-transform-
ation matrix for all transformations to the same S-base is equal for
all those transformations. ;
As this transformation matrix only depends on (rather good) approximate
values of the x- and y-coordinates of all points of the network (which
are available from the first phase of the adjustment), t is practically
always possible to obtain this matrix and thus to calculate the needed
c-vectors and the accessory boundary values.
So it is not necessary to carry out the whole adjustment on another
S-base.
3. THE BLOCKS THAT WERE INVESTIGATED
3.1 Three different block configurations were taken in consideration
a. a regular block consisting of 7 strips with 14 models per strip
which covers a square area of about 8 by 8 kilometers
b. a regular block consisting of 5 strips with 20 models per strip
which covers a right-angled area of 5.7 by 11.4 kilometers
c. a more or less irregular block which was created by omitting a
number of models from a regular block of 7 strips and 20 models per
strip.
More experiments were carried out
with 6 single tie-points per . e
model divided as shown in fig. I.
In the one case with 4 tie-points
only the corner points were used.
In the cases that 6 tie-points : 3
were used this meant that for the
three blocks the x- and y-co-
ordinates of 225, 231 and 241 e o
points resp. had to be calculated.
figure !
3.2 Values of block parameters
A number of block parameters are equal for all experiments and are
listed below
photosize: 23 x 23 cm
principle distance: 150 mm
photoscale: 1:6200 (common for cadastral work in the Netherlands)
model scale: 1:3200
forward overlap: 607
side lap: 207
The a priori v.c. matrix of the model coordinates:
