Visualisation - A Tool for Documentation and Investigation of Historical Buildings 
265 
3. THE CHURCH STEEPLES OF 
THREE EPOCHS 
As an illustration the CAD models of all three tow 
ers are put on a common model of the church build 
ing and therefore are able to be compared and to be 
judged by their architectural effect. The church 
building itself can be left in its current state referring 
to these reflections because it has stayed almost un 
changed in its outward appearance apart from minor 
changes in the choir area. The 3-dimensional model 
is built up on the basis of the stereorestitution. The 
deformations recorded in the survey are not taken 
into the model, because not only would they in 
crease the labour in a considerable way but also are 
they not relevant for the illustration. 
The tower in its original state was built as a Gothic 
roof turret and is documented in a few illustrations 
of contemporary painters. The oldest known descrip 
tion is a pen-and-ink drawing made by Augustin 
Hirschvogel in the year 1536 (Fig. 2) and a drawing 
by Christoph Lienhardt from about 1700 (Fig. 3). 
Here no precise measurements or proportions about 
the turret can be derived. But the comparison to an 
other Cistercian ridge turret of this epoch allows 
some conclusions about the size of the Salem turret. 
The monastery church of Maulbronn, Germany, also 
has a roof turret of this style, which is documented 
by stereometric photography (Fig. 5). These data can 
be used to reconstruct a model of the Salem tower. 
The second phase of construction resulted in a Ba 
roque tower of respectable size, whose history can 
already be traced through records in several files, 
such as drawings, paintings and archive notes (Fig. 
4). 
An exceptional feature is a still existing wooden 
model(Fig. 7) of the size of circa 0.7 x 0.7 m in the 
ground plan with a height of about 3.5 m, that refer 
ring to archive notes was built shortly before the 
construction of the tower. It illustrates the complex 
framework construction. For the reconstruction 
stereopictures are taken of the model. They are ana 
lyzed by stereoplotting and completed by hand 
measurement (Fig. 8), so that the model is docu 
mented in floor plans, elevations and sections. To 
determine the exact size this CAD model is fitted to 
the roof truss ground plan of the crossing according 
to today's appearance(Fig. 9). A scale of circa 1:15 
for the wooden model results. The form of the fa 
cades basically follows historical descriptions (Fig. 
4). 
The state of today's roof turret has not changed since 
1807. It is recorded by photogrammetry exactly 
(Fig. 6). The modelling of this form follows the 
same proceedings as described above. As a result of 
the visualisation we can regard three virtual models. 
Each of them is shaped in the same way and makes 
it possible to compare with each other (Fig. 11, 12). 
Fig. 5: Stereometric photography of the Gothic ridge turret 
in Maulbronn 
Fig. 6: Stereometric photography of the current turret