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precise and reliable 3D line parameters, especially for
those lines which are nearly parallel to the epipolar
plane, as their position in 3D will be fixed through the
intersection with other lines in two line points.
The introduction of a local coordinate sytem for the
geodetic method caused that no absolute coordinates
could be compared. The organisation of further tests
should be done in such a way, that this is possible. A
further point of criticism is, that not the real epipolar
angle in image space was used but an approximation,
the angle EPI. Therefore it was not possible to check
the vertical lines in respect to the variation of the
epipolar angle.
Our opinion is, that line photogrammetry can be used
with advantage as a tool for the calculation of man-
made objects after semi- or fully automatic localisation
of such objects in digital images. Therefore, and caused
by the promising results achieved in the tests done
here, investigations concerning the extraction of image
points for line photogrammetry using matching or
other segmentation methods in digital images will be
done in the future. Furthermore, all theoretically
derived constraints will be implemented and more
complex features will be tested in respect to their appli-
cability for this method.
6. ACKNOWLEDGMENTS
This project was made possible by the financing by the
department for photogrammetry at the Royal Institute
of Technology, Stockholm Sweden. The author would
like to express his gratitude to Prof. Dr. Kennert
Torlegärd for his guidance in this project. I also like to
thank Lars-Âke Edgardh and Anders Boberg for their
useful cooperation.
7. REFERENCES
1 Lugnani,]. B., 1982. The Digitized Features - A New
Source of Control. In: Int. Congress of Photogram-
metry and Remote Sensing., Taniemi-Japan, Vol.
XXIV Supplement, pp. 188 - 202
2 Masry, S. E., 1981. Digital Mapping Using Entities: A
New Concept. Photogrammetric Engineering and
Remote Sensing. Vol 48(11): 1561-1599.
3 Mulawa, D. C., Mikhail, E.M., 1988. Photogram-
metric Treatment of Linear Features. In: Int.
Congress of Photogrammetry and Remote Sensing.,
Kyoto-Japan, Vol. 27 Part B10, pp. 383 -393.
4 Persson, B., 1985. Linjefotogrammetri. Department
of Photogrammetry, Royal Institute of Technology,
Stockholm Sweden. Unpublished.
5 Sayed, A. N., Mikhail, E.M, 1990. Extraction And
Photogrammetric Exploitation Of Features In
Digital Images. Report CE-PH-90-7, School Of Civil
Engineering, Purdue University, West Lafayette,
USA
675
8. FIGURES
10 = 10
© 6
> 4 $
> i
ke] A 7 4
& 6
o S. 0i « Mi
g 8
: NE i:
& 001 T
12345678910112 1.2 3456 78
line number line number
Figure 3a: Figure 3b:
Figure 3a and 3b shows the results from test case a for
building A and B respectively The columns show the
mean of the standard deviation of the estimated angles
ô, ©, Y with (black) and without (white) the introduc-
tion of the geometric constraints. Line 1 to 8 of buil-
ding A and line 1 to 4 of building B are horizontal. The
vertical lines are line 7 to 12 for building A and 5 to 8
for building B.
f J f À
> >
zo NT
N N
001 001
123456789101112 123455871
line number line number
Figure 4a: Figure 4b:
Figures 4a and 4b shows the same test case as shown in
3a and 3b, but with the standard deviations of the esti-
mated metric parameter r instead of the angles 8, q, y.
[gon]
e
[gon]
=
mean of sdev.
=
T 1
> >»
L m
> >
» > ++
>
> d»
mean of sdev
01 or T v ¥ 01 T T T re
0 20 40 60 80 100 0 20 40 60 80 100
angle EPI [gon] angle EPI [gon]
Figure 5a Figure 5b:
Figure 5a and b: Measurements from test case b where
the mean of the standard deviations of the angles 8, q,
y are plotted, as a function of angle EPI. Results
without geometric constraints are plotted using crosses
(+) and triangels (A) are used for cases with constraints.
