correct choices at the different steps and eliminating the wrong
possible alternatives.
Figure 5. The 2 small blocks obtained after the model bridging
(the second one is incongruent)
7. NUMERIC EXPERIMENTS
To verify precision, accuracy and reliability of these techniques,
a program in FORTRAN 95 has been implemented and tested.
It runs on a Pentium 3 PC, with 933 MHz - 262 Mb / RAM -
30 GB / Hard Disk. The exhaustive research for the Symmetric
Relative Orientation works in 4 - 5 seconds, while all others
procedures are immediate. In all the examples, we introduced
random errors, with standard deviation of 20 um, as usual in
photogrammetry. Here we present an explanation of these
programs:
ORPHO it converts Cardanic angles in Eulerian angles and
vice versa. This is a very large used transformation in close
range photogrammetry, because it is essential for the image
orientation, when the rotation angles are acquired by surveying
measurements.
ORSYM it calculates the preliminary values for the Symmetric
Relative Orientation. It solves 12800 linear problems, exploring
all possible configurations in the space, with a step of II/4. The
same program, choosing one of the four distinct solutions,
permits to calculate the preliminary parameters for the
Asymmetric Relative Orientation.
ORELA it calculates the adjusted parameters of the
Asymmetric Relative Orientation, starting from its preliminary
ones. If these preliminary values are unknown at the data
acquisition, it is possible to get them from the results of the
previous program. On the contrary, if they are already known, it
is possible to transform the Eulerian angles, more frequently
and easily acquired, into the Cardanic ones, by means of
ORPHO program.
ORABS it calculates the adjusted Absolute Orientation
parameters. They are calculated with a simple substitution of
variables, which is able to transform the non-linear problem of
the Absolute Orientation in a linear one.
Let us summarize the global procedure for the orientation of
two images, viewing the flowchart (Figure 6).
With the new procedure, we eliminate any human intervention
after the starting inputs. For that reason we unify all the
Orientation programs in one called ORTRE. This program can
run automatically and is able to find the adjusted parameters of
the Absolute Orientation. In the follow flowchart (Figure 7) we
want to show how all the global procedure run after the starting
inputs of three images.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004
SURVEYING
MEASUREMENT AND
(CLASSICAL)
PHOTOGRAMMETRY
NON-CONVENTIONAL
PHOTOGRAMMETRY
SELECTION OF
AN ACCEPTABLE
SOLUTION
y
PLOTTING
Figure 6. 2-image Orientation — Global Procedure
3-images input
ORSYM 1-2
4 models 1-3 |
4 models 1-2
Dé
| BRIDGING |
GE Enc
16 solid structures
ORSYM 1-3
ORABS
ONLY ONE
ACCEPTABLE
SOLUTION
Figure 7. 3-image Orientation — Global Procedure
(ORTRE Program)
As evident, the analysis of the performance of the single
programs and of the global procedure was quite heavy. Indeed it
needed a long preparation of tools, which permitted to manage
files of commands. Furthermore many different levels were
prepared in order to collect, save and store the output files for
the different steps.
8. CONCLUSION AND FURTHER DEVELOPMENTS
A solution to solve for the problem of object reconstruction
from three images not requiring any initial approximations for
orientation parameters has been proposed. The procedure is
based on the classical two steps approach of photogrammetry,
i.e. relative and abgolute orientation. All possible combinations
of image pair in the triplet are considered and relatively
Inter
—
regis
(Mus
amor
the
origi
true
recot
for \
abov
Adv:
imag
respe
resul
algoi
furth
techi
with
estin
Leas
them
rand.
coml
devi:
Torr
Seco
of t
phot
ofm
on |
relat
para
seve
respi
relat
Con
imag
thre«
the
rese;
beca
prev
Fina
nece
Refe
Fins
Phot
Vere
Four
Roy
Hatt
App
pp. €
Heiy
Orie
Kru
mit
Kl. (
Lon,
à sc
Pan.
Orie
