CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
255 
Airborne survey 
It is traditionally associated with cartographic representation. 
Today the distinction between cartography and architectonic 
survey has many overlapping areas. One clear example is the 
survey of paving at a 1:200 scale. 
The survey carried out by the work group led by Professor 
Carlo Monti (Milan Polytechnic) was made in large part using 
aerial photoplans at a scale of 1:10000 and for the shady areas 
with ground shots from scaffolding. The one hundred thousand 
stones in the floor were rectified with an accuracy of ±3 cm. 
In this case, the nominal scale is the same as architectonic 
survey even if the technique and the representation are 
cartographic. 
Representation is a planimetry and not a plane which we know 
is a horizontal section at a given height, while planimetry is a 
view from above. 
The survey of the floor takes its place among the other vector- 
cartographic representations of the square: the City Technical 
Map (CTC) is at a scale of 1:500 and the Regional Technical 
Map (CTR) is on a 1:5000 scale. These are congruent with each 
other since the CTR is obtained from a simplification of the 
City Technical Map and therefore the metric accuracy of the 
signs on a 1:5000 and is the same of the 1:500 scale. 
The aforementioned maps are available for the square: 
• 1:5000 
It is thus possible to overlap the cartography described 
previously and the DEM obtained by laser scanner (fig. 4). 
It was interesting to note that despite the accuracy of the 
altimetric data, about ±50cm, from a rapid elaboration and 
using the Kriging algorithm for the gridding and therefore, 
having generated the level curves, it was clear that the progress 
of the square is characterised by its well-known "mule's 
humps". From a comparison with the curves obtained with 
trigonometric levelling, we found how the elaboration of the 
laser data give optimal results. 
It was decided to construct a true orthophoto of the area of the 
Square. In the study, the 1:500 scale numerical cartograpy was 
used for planimetric information and laser data for the 
altimetry. 
The existing numerical cartography was edited to extract four 
different level of closed areas: 
1. main pitches (main roof structure) 
2. secondary pitches (garrets, etc.) 
3. main streets 
4. bridges, small narrow streets, etc.. 
Respect these different categories, the geo-referred laser data 
was processed to obtain the dense DTM (18 cm) used as a basis 
for realisation of a true orthophoto (fig. 5). The photograms 
used were made by the CGR and supplied with the orientation 
parameters registered during the flight. 
• 1:500 
• 1:200 
all refer to the same reference system. 
The first two are simply planimetric maps while the map on a 
1:200 scale is three-dimensional. The altimetry of this latter was 
integrated with the terrestrial measurements for trigonometric 
levelling on a 4x4 regular grid, traced on the ground and 
successively interpolated on a lxl meter grid. 
The levelling served to realise profiles of the square at a scale 
of 1:50 for the study of problems related to flood waters. 
The DTM have given the level curves introduced in the 
cartography. Thus, we were able to obtain a map at nominal 
scale of 1:200 in planimetry and altimetry (fig. 1). 
As regards the buildings that encircle the Square, we have no 
altimetric data from the city and regional technical maps. 
Therefore, these were integrated with ground measurements in 
order to obtain a volumetric 3D model of the Square. 
Recently a test flight from the CGR was realised with the 
TOPOSYS laser scanner system that has supplied a new model 
of the heights of the WGS84 reference system. The flight was 
successfully georeferenced with respect to the national system. 
—!■ 
fig. 4 Laser Scanner data elaborations (mesh and elevation curves)