4.2 Surveyed data 
We set up 12 scanning stations, for a total of about 12.458.302 
measured points. The following table describes the scans. 
scan 
number of 
surveyed 
points 
max 
distance 
on natural 
point 
distance 
between 
scan and 
GPS 1 
distance 
between 
scan and 
GPS 2 
distance 
between 
scan and 
GPS 3 
1 
2.078.835 
258,61m 
26,09m 
56,47m 
29,52m 
2 
1.274.512 
128,51m 
29,49m 
36,63m 
56,43m 
3 
625.892 
260,06m 
36,61m 
45,44m 
75,31m 
4 
1.106.637 
455,69m 
48,80m 
63,90m 
73,28m 
5 
1.332.457 
204,65m 
33,31m 
155,91m 
13,73m 
6 
425.173 
149,47m 
155,91m 
- 
- 
7 
447.037 
118,06m 
- 
- 
- 
8 
973.540 
331,38m 
106,36m 
29,58m 
35,67m 
9 
648.613 
132,37m 
26,59m 
22,66m 
39,79m 
10 
1.508.824 
235,39m 
72,84m 
47,32m 
28,70m 
11 
1.061.557 
162,99m 
44,85m 
89,50m 
46,78m 
12 
975.225 
214,27m 
28,55m 
47,22m 
127,47m 
Table 2. Information about the clouds surveyed 
Stations 6 and 7 refer to measurements of a terrestrial surface 
with low satellite visibility. In fact, it consists of a narrow road 
bordered by tall buildings. In this case, as in similar ones, we 
decided to use the maximum number of positionable antennas 
(e.g. only one antenna was positioned at station 6) and the 
classical recording method (i.e. application of flat targets in a 
zone of overlap between two scans). 
5. RESULTS 
5.1 Recording of the scans 
All the scans were analysed on the basis of our experience in the 
previous studies; in particular, before starting to record, it is 
fundamental to perform a control and possibly a manual 
adjustment of the recognition of the target centres proposed by 
the scanner. 
It is also appropriate to cancel all the erroneously acquired 
information due to disturbances (e.g. pedestrians and moving 
vehicles), so as to make the model as legible and interpretable 
as possible. 
We then used the recording procedures included in the 
dedicated software and we evaluated the resulting three- 
dimensional residuals by subsequent application of the 
calculated transformation. 
The coordinates of the phase centres of the GPS antennas were 
transformed into local topocentric coordinates centred on the 
master; in this way, we could directly apply the offsets between 
the target and phase centre of the antenna. 
We now report the results in a frequency histogram with 1 mm 
classes: 
As can be seen from the histogram, 67% of the residuals are 
smaller than 6 mm, which is the manufacturer’s stated precision 
of the laser scanner for acquisition of a single point. 
67% 
r-CNCO-tiOcpscpcnQT-CMfO^intONCOCfJOr-tNMTtin 
Or-cMcO'tiotDh-(¿TTT' T 7' r 7 T 7 T 7 T 7 T r , 7 c ^ c í lc ^ c í ,c ^ c í J 
0)Or-CNl<OTfl/)(OSCOO>Or- CNÍCOTT 
0-6 mm 
classes [mm] 
Figure 9. Histogram presenting 3D residuals’ module 
5.2 Data analysis 
We now report some visualizations of the point clouds. 
Visualization in raster format prevents the recognition of much 
information which instead is perfectly interpretable by direct 
analysis of the three-dimensional data. 
In figure 10 and 11 we show two single scans; the arrows point 
out the position of G.P.S. antennas and adapter. In figure 12 we 
show the model after the merging of the two scans. By using 
this procedure many times we obtained the entire model. 
Figure 10. A single scan. The arrows point out the position 
of the G.P.S. antennas 
Figure 11. A single scan. The arrows point out the position 
of the G.P.S. antennas