art B5. Istanbul 2004
ied methods are put
kia tb =ocatenary
of k. F.. mp — the
ponent and its error,
based on equation 2
rrorless).
ing algorithms were
owest my, is the only
ermines the catenary
eceived by the new
1 is the same for all
cal photogrammetric
nce is of no practical
w the real tension
ethods have proved
1g is that the value
range of the values
my Fr [N] Mpx
[cm] [N]
3.8 | 457.0 |. 0.3
6.9 | 458.0 | 0.6
42 | 457.0 | 04
'd results.
ing algorithm results
very simple analysis
resolution of the line
r of the rope position
1, with the assumed
have 1.1 jum, which
| size).
method precision for
F the table. The result
uch attention to, as it
lifferent scales will
xel resolution. More
with different scales
le conclusions.
letermination of the
borated and practical
stem is based on the
en adopted in new
ing has also been
is to be satisfied for
2). This also requires
aptop, digital camera
ject), and a picture
ible connection). An
rt of the system. It
ation, control points
e ropes in the image,
uting of the tension
strength. The program works under the supervision of a human
operator. The operator performs the above mentioned
measurements and decides about proceeding to the next step of
processing (after the previous stage has been finished).
Some further conclusions and information about the system are
listed in points below.
e The rope image has to be wide enough to be able to
run the line following algorithm (at least 7 pixels), i.e.
scale factor (m,) should be appropriate,
e An automatic measurement of the rope is most
reliable in areas with a homogenic background and a
good contrast between the rope and the background
(e.g. the sky in the background); such 1deal situation
does not constitute a rule, which is why further steps
should be made,
e The filtering algorithm has been elaborated in order to
deal with miscalculated points; practical results of the
work of this algotithm have been promising.
e The results received by the new digital method are
similar to those received by the traditional method but
the error is smaller. This can be explained by a large
number of well-fitting points (21600) used for the
estimation of parameters,
e The new technology shortens the time of the process—
after control points have been set out and their
coordinates have been determined, the whole process,
from the taking of the picture to the receiving of the
result, takes only a few minutes,
e The system works almost in real time, which is why
correction can be done onsite and the whole process
can be repeated as many times as required,
e The sub-pixel resolution of the line following
algorithm was evaluated at «0.12,
e The photogrammetric method’s advantage — short
registration time of the whole rope - may be used for
a more complex treatment of the tower and its ropes;
all objects registered in one picture allow us to
calculate tensions in all ropes and, possibly, even
check the tower verticality for one moment in time.
This can be possible in the future; at present,
however, sensor resolution is still limited.
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