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New perspectives to save cultural heritage
Altan, M. Orhan

CIP A 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
Table 2. RMSE of 3D ground coordinates of the check points in
digital image (units are mm)
The rectification was conducted before the stereo matching to
decrease the parallax which could induce the disparities of the
pixels of the same position. Right image is rectified to left
image using ERDAS IMAGINE 8.4. Inverse transform equation
is following equation :
X'= 1.3026X + 0.172982 Y + 54.8103 (])
Y'= 0.0862574 X + 1.04515 Y - 79.7225
where X, Y = rectified pixel position
X\ Y— inverse transformed pixel position
cross correlation method for stereo matching was performed.
Then we can get the 3D point cloud pixel using the analytical
space intersection with interior, exterior orientations and
inverse transformed pixel position.
3D model can be generated using Rapidfom2002 (Figure 5.).
Figure 6. DSM extracted from the data acquired from laser
scanning (left) and stereo photogrammetry (right)
3.2 Comparison
Dark area means an accordance of the two DSMs. White area is
the region where the error is over 74.368 mm. Coefficient of
correlation of these regions was represented low value.
It is possible to classify the two regions (Figure 8.). One is for
the shadows and the other is for the large parallax. The region
affected by shadow is arised because the direction and intensity
of sun light on getting the left image were different from those
on getting the right image (region B).
The region affected by parallax is arised because the parallax
can be too large at some part, like A and B. It is possible to see
the effect of parallax on the image matching from Table 3.
Figure 5. Screen capture from Rapidform2002 program for
building the digital elevation model using the data
acquired from stereo photogrammetry
3.1 3D modeling
It is possible to the difference between the two methods from
the results. Figure 6 shows results from each method.
DSM by S25 laser scanner is used as the reference data for the
analysis of result by digital stereo photogrammetry. S25 ensures
an accuracy that is the standard deviation of 0.21mm in 0.8-10m
measuring distance.
Heightss of both DSMs can be detected by overlapping the
DSM from digital stereo photogrammetry on the DSM by laser
scanning (Figure 7.).
Figure 7. Height differences between laser scanner DSM and
photogrammetry DSM (units are mm)
Figure 8. Target region