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generated by the StereoView digital photogrammetric package. 
The same program, but in this case with some manual editing of 
the original 5 mm grid, was adopted for the surface modelling 
of the masks from the Big Fountain nymphaeum; the results for 
the left mask is shown in figure 4. The automatic 2 cm grid 
DSM, after some a-posteriori manual correction, has been the 
base for the orthophoto of the facades; a particular for the upper 
part of the Small Fountain front is represented in figure 5. 
Finally, figure 6 shows, using a simplified 3D reconstruction, 
the results of mosaic composition for the digital rectifications 
(software Rollei MSR rel. 4) of the walls located nearby the 
Small Fountain nymphaeum. 
Fig. 4 - Particular from the House of the Big Fountain: the 
mask on the left part of the nymphaeum, (a) Raster 
image depicted on the DSM obtained by automatic 
correlation, with grid and breaklines; (b) final 
orthophoto. 
Fig. 5 - House of the Small Fountain: 1:25 digital orthophoto 
for the upper part of the front (reduced). 
Fig. 6 - Mosaic of rectified images for the walls nearby the 
Small Fountain nymphaeum in a simplified 3D 
reconstruction. 
2.2 Laser scanning 
For the two above mentioned nymphaea a laser scanning survey 
was realized by using the Riegl LMS-Z210 system (fig. 7). This 
system can perform data acquisition for objects at a distance 
from 2 up to 350 metres, with a nominal accuracy in the 
distance of about 2-2.5 centimetres. Different systems could 
guarantee a better accuracy on short distances and could 
provide perhaps better results for an object of this dimension. In 
archaeological or architectural situations involving a large range 
of working distances this product could however allow a wider 
assortment of applications. 
Fig. 7 - Big Fountain nymphaeum: laser scanning for a lateral 
station. 
The system is able to acquire intensity, range and also RGB 
images for a scanning range of 370 gon (horizontal) x 88 gon 
(vertical), with a minimum angle step resolution of 80 mgon, 
either in horizontal and in vertical. 
The definition of a Cartesian world reference system for the 
point coordinates, otherwise expressed in the polar system, can 
be performed in different ways: 
using the standard instrumental orientation; 
by a coordinate system described by a specific plane and 
one axis or, in alternative, the origin and the normal vector 
of a second plane (method useful for the registration of a 
single scan); 
by a manual modification (move/rotate) of the actual 
coordinate system;