CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
473 
ation 
have 
oject of 
mesh 
of the 
all the 
lumes of 
/een the 
emulate 
ways of 
ument to 
Ways of 
only the 
beams 
plitude) 
of any 
models 
images in 
The two 
/green or 
means 
aration and 
(black 
asses) 
As said, anaglyphs can easily be obtained from stereopairs of 
photographs, but it is also possible to render them from three- 
dimensional drawings. Some CAD systems like Microstation®, 
allow the visualisation of stereo-images which can show a 
realistic three-dimensional simulation of the relief. The interest 
of these views lies on the fact that they transmit new sensations 
in the observation of objects and they are, without any doubt a 
great instrument to call the attention of the public on the 
heritage assets. 
5.6 Realistic visualization, ortho-rectification. 
In the field of 
Cartography, DTM are 
very often used to obtain 
ortho-photographs of the 
terrain. These are achieved by 
the projective transformation of 
differential local areas in one or 
several images with the help of a 
mathematical frame offered by: 
1. That of the 
lattice work of the 
DTM. 
2. Interior geometry 
of the camera (lens focal 
length and the lens distortion 
parameters) as estimated 
from the camera 
Calibration). 
3. The exterior orientation 
parameters of the image: 
The position vector (3 
parameters per image) and 
orientation (3 parameters per 
image) of the camera at 
exposure times. 
The objective of differential 
rectification is the assignment of 
grey/colour values from the 
image to each cell of the DTM. 
Notice that the need of internal 
parameters of the camera is an 
obstacle to the use of conventional or non-calibrated cameras. 
The ortho-image is a document which has not only the metric 
properties of a plan but also the power related to the qualitative 
information content relative to a photograph. However simple 
rectification would be more advantageous in financial terms if 
the object is flat enough. The generation of digital surface 
models enables the obtaining of orthoimages but, we must say 
that, in general, it is not very profitable. 
possibilities that we have managed. There could be many other 
applications. 
In any case we must admit that the effort needed to get accurate 
and detailed models my means of restitution of features without 
thematic meaning (breaklines and random spots), makes them 
expensive and sometimes unaffordable. 
As you all could probably think, all the related possibilities 
could be better achieved by the surface models obtained with 
laser scanning devices... well, we must agree. But by this time 
these machines are not capable to make full-satisfying feature 
extraction and still need to work in combination with the classic 
more human-guided Photogrammetry equipment. 
5.7 Curvature Maps 
Curvature of the surface form is a measure of the rate of change 
of slopes. This could give us an idea of the distribution of 
weathered areas. These are zones of the object where edges are 
getting eroded showing different stages of decay or show a 
significant loss of high frequency detail. 
6. CONCLUSION. 
We have widely tested the utility of digital surface models in 
the context of Architecture and tried to highlight a few