In 
Transformation equations 
The relative position of the fiducial marks has been determined with a pre- 
cision stereocomparator in all the cases that have been denoted with the sym- 
bols N 
tions that have taken place in the material have been examined by relating the 
1° PE D,, » and K of the paragraph on "Tested Material". The deforma- 
fiducial mark rectangles to each other using the following two groups of trans- 
formation equations: 
x.= 8, * jy! - Sox 
(1) 
=< 
Il 
bo + ay + ax 
and 
x28 t aQX' t a,y! 
0 1 2 
(2) 1 1 
y bo + b,x + b,y 
Equation group (1) is the general Helmert transformation and includes trans- 
lation, rotation and a change of the scale resulting in 4 unknowns. Equation 
group (2) is the so-called affine transformation and includes translation, ro- 
tation, a change of scale in such a way that the scale differs in the direc- 
tions of the x- and y- axes, and a correction of the right angle between the 
coordinate axes of the system that is to be transformed, resulting in 6 un- 
knowns. As there are a total of 8 measured quantities the coefficient to be 
determined are calculated by the method of least squares. 
Performed transformations 
All the performed transformations are given in table 2. The transformation 
symbols denote the measurements that have been compared and the letter H in 
front alludes to the equation group (1), i.e. the Helmert transformation, and 
correspondingly A to the affine transformation i.e. the equation group (2). A 
total of 8 Helmert and 8 affine transformations have been computed. The re- 
sults of the transformations are given in table 3. 
The first row of the table gives the fiducial mark numbers 11, 22, 33 and 44 
and at the left the first column depicts the numbers of the nine photographs. 
In addition to the transformation symbol each table is denoted with a symbol