4. Module of Orthophoto Generation 
At this point, generation of an orthophoto comes about fairly 
easily: for each pixel of the empty image (the future 
orthophoto) the x,y,z co-ordinates are known. These co- 
  
       
ordinates and the DLT parameters give the pixel corresponding 
to the non-metric image. The radiometric value of this pixel is 
transferred to the empty image. 
= JO] x] 
  
  
  
  
Z iniziale lunghezza . altezza passo 
[os ^ [250 au | [i300 — [1390 — [oon [Ezio [0.3693 [sim ini Load DTM 
‘mir Ymas —À xmmeg | vimnag GetXYZ || — Othe 
| 1.000 [170141638 Auto Y | Aggioma | La I | [ eece expDTMrot | Save orthoimm 
  
  
  
  
  
  
  
  
  
  
Figure 11: Ortophoto referred to the columns plane (plane I) 
In addition to generating the digital orthophoto, the depth of the 
pixel is memorised, in other words, the Z co-ordinate with 
respect to the XY reference plane. The result is an orthophoto 
where for each pixel, the value of the third dimension is known. 
The advantages of the metric orthophoto on the plane and the 
digital model of the heights are joined: it is possible to measure 
distances on the projection plane as well as in space. 
In order to check the final concordance of the information 
processed, the software enables simultaneous identification of a 
single point in three windows: ortho image, laser image, non 
metric image. 
The test 
Collaboration with INOA (Istituto Nazionale di Ottica 
Applicata), has permitted evaluation of the application of 
optical techniques in the three-dimensional reconstruction of 
objects having significant historic and artistic interest, at 
different scales and with different purposes: from the survey of 
wooden matrices using conoscopic holography to survey of 
statues or portions of architectures by using different laser 
techniques. 
From analysis of the experiments conducted by other research 
teams, from the expertise of the authors in the field of survey of 
monumental objects, and the knowledge of the INOA in the 
field of laser scanning of works of art, we have reached a 
definition of a TOF laser prototype with technical 
characteristics very comparable to the instruments currently on 
the market. 
In the definition, we made a series of design and operating 
premises. The instrument works like a theodolite and therefore 
like this instrument, it must be equipped with a system of 
adjustments able to rectify and put them in range. Included in 
the realisation of the instrument are a striding level, a tribrach 
with bull’s-eyed bubble and the mechanical adjustments 
necessary to achieve the intersection and the diagonality of the 
three fundamental axes of the system with precision comparable 
to the precision given by theodolites. 
Experimentation was conducted in the Michelozzo courtyard of 
the Palazzo Vecchio, in Florence, comparing the prototype to 
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