APPLICATION OF DIGITAL PHOTOGRAMMETRY AND IMAGE PROCESSING
TECHNIQUES FOR HYDRAULIC MODEL EXPERIMENTS
M. Sedat Kabdasli ^ *, T. Murat Celikoyan *, Dursun Z. Seker“, Alparslan Aydingakko *
“ITU, Civil Engineering Faculty, 80626 Maslak Istanbul, Turkey - (skabdasli, mcelikoyan, dzseker, agakko)@ins.itu.edu.tr
KEY WORDS: Bathymetry , Modeling, Orthoimage, Photogrammetry, Hydrology
ABSTRACT:
Stability and suction removal of the sand bed under the rock-armoring layer were exposed under the wave and discharge generated
steady flow and coexisting flow investigated at apron area of the open channel discharge system. Determination of the stability of the
armoring layer was achieved by micro and macro scale tests focused just sample stone(s) and all armoring area in 1/25 scale
laboratory physical model. In this study, two methods are used in order to investigate probable displacement caused by the water
flow in a hydrological experimental setup. The setup is a scaled model of an harbor in Omman, UAE, which is already in
construction. Both methods are dealing with photos taken with a digital camera. The photos are taken in four epochs. The first epoch
of photos has been taken just after the construction of the experimental setup. This causes the first epoch of photos to be the
reference set. Between the following three epochs, an hydraulic experiment has been taken place. Comparison these three epochs of
photos with reference set and each other results the investigated probable displacement. The data contains all the photos and the
terrestrial measurements. The difference of methods is the processing of the data. The first method is the standard photogrammetric
method, where the second one deals much more with image processing. The results of these two methods will be compared with each
other in order to give accuracy. Image processing techniques was applied at macro scale tests of the armoring area before and at the
end of the experiments. Instability was not determined for whole armoring layer after the both image processing processes and
photogrammetric approach.
1. INTRODUCTION
One of the methods widely used for scour protection in coastal
engineering is rock dumping on a sand bed. When such a rock
layer (armoring layer) is exposed to steady current, waves or
ce
combined flow their stability are an important issue for
engineering design. (Cokgor, et.al., 2004). The design of stable
bottom with movable material such as sand, gravel and stones is
the most difficult problem of the coastal engineering because of
the lack of analytical solution (Kabdasli, 1986) However the
definition of critical conditions in which the movable material
can be moved by hydrodynamic forces created by current waves
or combined effects of them (Kabdasli, 1990), the processes are
highly chaotic in nature. For this reason experimental studies
are needed in order to obtain the material characteristics such as
shape, size, etc. which can be in stable condition under design
hydrodynamic conditions.
On the other hand, experimental studies are very difficult and
time consuming works because measurements and observation
of the material motion are highly complex techniques due to
randomness of the material transport. Particularly experimental
study for a coastal area is almost impossible by using classic
measurements techniques. In that case, alternative. methods
should be used in order to reach reliable results. It is clear that
digital photogrammetry and image processing techniques are
the most favorable methods. In order to determine probable
displacements or deformations, some methods have been
discussed in Altan, 1981.
In this study, stability armouring layer against erosion over the
sand bed of open channel thermal discharge system of the
power plant in an industrial area in Sohar, Emirate of Oman,
* Corresponding author.
was performed. Sohar is located nearly 200 km. North-West of
Muscat, capital of Oman.
2. DATA AND METHOD
Hydraulic model of outlet structure was built at 1/25 geometric
scale. The wave basin in the laboratory has dimensions of
25x28xl m. Stone pitching was used at the sea bottom between
-0.5 m and —2 m elevations. Discharge channel was constructed
of concrete and brick walls (Figure 1). Main issue at the model
study was the determination of the stability of stone armour
layer on the sand dredging channel in the sea. Various flow
measurements and observation techniques were used in the
model tests.
For modeling the experimental setup, terrestrial surveys have
been done. A terrestrial reference point set has been marked so
that they surround the experimental setup and using these points
the modeling process has been done. The reason of marking the
points surrounding the experimental setup is the inner coverage
of the model. The setup is covered with small stones and this
would cause the reference points to be displaced by water flow
during the hydraulic experiments. Because of that, points have
been marked onto concrete bottom, so that they would not be
displaced. These reference points will be used control points in
photogrammetric evaluation. These points have been colored
with red, so that they could be seen clearly without any
reflection. Figure 2 illustrates the distribution of the control
points with corresponding point numbers where Figure 3 shows
an overview with a zoom-view for control point.
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