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Figure 3. 
Altimetric scheme of photogrammetric stations 
As confirmed by the first survey, each order 
should be considered as a separate element limited 
by the plane of best fitting of the points 
surveyed on the dripstone. 
We used a Wild AC1 for the restitution and, since 
our aim was to produce a mathematical model of the 
Tower, we set up a data base into which we filed 
the information to be processed. 
After comparing the data obtained by plotting 
monochrome and color photographs, we found that 
the latter gave a more accurate collimation of the 
points surveyed. After a careful analysis of 
images available, six pairs of stereo-photograms 
were chosen for plotting. These were numbers 1 and 
12; 2 and 3; 3 and 4; 5 and 7; 8 and 9: 11 and 12 
(Figure 2). 
The remaining images will be used in a future 
project that will focus on the details of the 
Tower. 
For the absolute orientation more than seven 
control points on the Tower were used. The 
orientation protocol shows that the maximum 
residual was 0.4 centimeters. 
The points surveyed and the way they were codified 
is shown in Figure 5. The codes LV20 and LV21 
refer to the points surveyed on the two edges of 
the first order dripstone, while LV30 and LV31 
relate to the second order, and so on. 
  
Figure 4. 
Pair of stereo-photograms