CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
The user, taking into account the unevenness of the surface to 
be measured and the degree of accuracy desired, will be able to 
establish the size of the tessella, resulting in a network which 
could be more or less dense which will adapt to the surfaces of 
the object quite accurately. Once this lattice has been obtained 
the software will allow to calculate the approximation of the 
volume of the original figure as the summation of the partial 
volumes of prisms whose bases are each one of the grid squares 
and heights are the average of its four corner elevations. 
By applying this technique we could calculate the volume of 
the loss of matter caused by weathering processes. If it is 
possible to rebuild (draw) the original shape particular to one 
piece, we will be able to obtain a digital model of its surface 
and facing to the model resulting from its current estate, 
obtained from the restitution, we will be able to obtain the 
volume between both states (Fig. 5). 
5.3 Deformation maps. 
One of the main aims of the terrain digital modelling 
programmes is that of obtaining, in an automatic way, a 
representation of the relief through contour levels, that is to say, 
maps of isohyets. These should make reference, in the case of 
terrains, to a particular altitude origin. If we make this 
application extensive to a given flat surface, we will be able to 
obtain a map of isohyets representing how the surfaces differ 
from that of reference (ideal plan) as if they were elevations of 
the ground surface. These maps can be drawn with different 
colours to highlight its expressive power this is an excellent 
way to represent areas which have been deformed or thrown out 
of plump. 
Figure 6. Colour depth map. 
The assessment of the degree of strain on the whole plan and 
not in isolated spots allows for a more accurate diagnosis of the 
nature of the cause. 
The same technique will allow us to represent any quantitative 
variable that has relevant spatial distribution. For example, if 
the elevation is substituted by the degree of humidity in several 
spots in the façade, we will obtain a map of the humid areas, 
etc. 
5.4 Simulation of shades, ilumination 
testing. 
The surface digital models obtained have 
been applied to the illumination project of 
the aqueduct. The triangle mesh 
reproduces the textural features of the 
surfaces of the ashlars and above all the 
combination of the rusticated volumes of 
their sides and the joints between the 
ashlars. This makes it possible to emulate 
the effect of the different ways of 
illuminating the given monument to 
enhance the chiaroscuro effect. Ways of 
illuminating differentiated not only the 
configuration and nature of light beams 
(colour, intensity, fuzziness, amplitude) 
but also by the spatial distribution of any 
number of sources. 
Figure 7. Solar Shadows simulation. 
5.5 Creating anaglyphs. 
An interesting product derived from the digital surface models 
are anaglyphic stereograms. These are stereo pairs of images in 
which each image is shown using a different colour. The two 
images are overlapped and then viewed using red/green or 
red/blue glasses (depending on the colours used). This means 
that the colour channel is used for the stereo separation and 
therefore the perception of anaglyphs is monochrome (black 
and white), although colour anaglyphs can be made. 
Figure 8. Anaglyphic stereogram, (use red-blue glasses)