International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004
3. MODELLING OF SURFACE ROUGHNESS BY USING
DIGITAL PHOTOGRAMMETRY
Developments in computer (software and hardware)
technology, as being in all other sciences, have produced
important structural changes in photogrammetry. Systems
known as digital photogrammetry minimizes workload, high
costs and time loss, are created by using high tech (hardware
and software). These systems resulted in variation of their
application fields and are important step into especially core
databases for information systems and digital map production.
The aim of this study is to measure the discontinuity surface
roughness using digital photogrammetric method. For this,
discontinuity surfaces are analysed as separate lands and the
heights of hills and that fill the surface are measured digitally in
3-D environment. In the case study, a sample of andesite having
7,75 x 7,75 cm measures is used and these processes are carried
out in three steps [Unal, 2000]. These are:
e Taking stereo photos by a digital camera
e Evaluation of digital photo pairs by computer software
and determination of surfaces coordinates (Figure 1)
e Obtaining three dimensional roughness map of the
surface (Figure 2) according to the acquired surface
coordinates by using graphics software
Firstly, photo-taking conditions shoul be determined for 3
dimensional modelling of surface roughness by following the
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scope of this study. These are briefly listed below as [Seker ve
Tavil, 1996: Unal vd.,2000]. This:
e Using a camera that is suitable to the aim of this study,
e Denoting and determination the object coordinates (at
least at 4 points) on sample surfaces for the evaluation
process,
e Arranging photo pairs by taking photos from different
points for three dimensional modelling,
e Taking photos so as to take, to capture all the details of
the surface.
Pictures acquired by a half-metric camera (Polaroid PDC 2000
/40) are appraised numerically according to the
photogrammetric principles by the help of digital
photogrammetric system. As a result, 3 dimensional map of the
discontinuity surface is produced.
When arranging photo pairs in order to determine surface
roughness, the care was taken for the range between camera and
the object and also to the base interval regulations, because of
the smallness of sample measures. Photo- taking were carried
out in two different points. Distance between camera and
specimen surface is 25 cm. In first and second camera positions
sample is held constant and photo taking device is moved when
finishing the photo taking. As the measures of sample decrease,
photo device is held constant and sample was moved.
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1D:2, x:0.004, y:0.070, z:0.029 , Objektpuni =
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1D:4, x:0.008, y:0.071, 2:0.020 TRIER =
|1D:5, x:0.009, y:0.072, 2:0.016
ID:6, x:0.012, y:0.072, z:0.016
1D:7, x:0.014, y:0.072, z:0.015
ID:8, x:0.015, y:0.072, 2:0.010
10:9, x:0.017, y:0.073, 2:0.007
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Figure 1. Description of the measurement of x ,y, Z coordinates of joint surface by using PICTRAN software
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