CITA 2003 XIX’ 1 ' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
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of two ‘arches’ are presented in Fig. 6, along with the original 
images. Perspective deformations have been removed, thanks to 
the adopted modeling scheme. Finally, Fig. 7 gives the full 3D 
model of the area and the resulting orthomosaic. 
Figure 6. Images (left) and corresponding orthoimages (right). 
Figure 7. Shaded 3D photogrammetric model and orthomosaic. 
These examples, also founded on the experiences from previous 
projects presented in Mavromati et al. (2002), indicate that the 
adopted strategy is suitable for geometric image transformations 
of both geometric accuracy and visual quality. As pointed out 
above, object location and surroundings actually ruled out any 
thought of experimenting here with laser scanning. To this end, 
a site was surveyed which had already been fully mapped pho- 
togrammetrically (Karras et al., 1999; Mavromati et al., 2002). 
4. EXPERIMENTS WITH LASER SCANNING 
For this archaic site in Athens, 7 images were chosen which had 
been acquired vertically with a small format camera and 28 mm 
lens (scale 1:1100). The mean RMS error in XYZ for 100 control 
points was 3.7 cm (five times smaller than that of the solution 
without correction of lens distortion). The site has very irregular 
relief w.ith successive vertical ‘falls’ and a marked slope. Photo 
grammetric point and breakline collection was performed in the 
mode described above. The resulting surface model and the or 
thomosaic were very satisfactory indeed. In Fig. 8 one can see a 
shaded view of the 3D model. 
W 
Figure 8. Part of the shaded 3D photogrammetric model. 
Fig. 9 shows an image of the object together with a further view 
of the shaded model showing the success of reconstruction. 
Figure 9. View of the object and shaded 3D model. 
The site was surveyed using a CYRAX 2500 scanner at a resolu 
tion of about 5 mm. A total of four stations were used, of course 
not enough for wholly capturing the object but sufficient for the 
experiment. Point clouds were automatically triangulated within 
a commercial software package, to provide a direct (‘unedited’) 
support for orthoprojection, which would then be compared to 
the product from the photogrammetric surface model. While all 
relatively smoothly shaped areas were orthoimaged in practical 
ly identical manner from both sources, this was not the case at 
the edges. Indeed, ‘vertical’ triangles were slightly deformed, as 
is clearly seen in Fig. 10. This resulted in image ‘blurring’ and 
‘erosion’ in the vicinity of discontinuities. Examples are given 
in Fig. 11. As noted by Bitelli et al. (2002), use of laser-derived 
models for orthophoto generation does not directly give satisfy 
ing results (depending on shape, data density etc.); thus editing 
of the model is needed, particularly as regards discontinuities.