NKEN
a. Its wreck has
Black sea. The
e realized using
will contain the
ite the model of
77 years, at the
ons of an open
e of Istanbul at
Military Naval
arine
build at the AG
in 4 September
ntinople Flotilla
9 tons during its
|. Submarine
The Technical Information for UB46 from archives is as
follows: (WWI U-Boat Types)
Length (m) 36.13 oa, 27.13 ph
Beam (m) 4.36 oa, 3.85 ph
Height (m) 7.34
Range (miles/knots) 6650/5 sf, 45/5 sm
Speed (knots) 9.15 sf, 5.81 sm
Torpedos 6
Mines no
Max.Depth — ca. 50 m (164 feet)
Crew 23 men
Power (hp) 284 sf, 280 sm
sm=submerged sf- surfaced ^ ph- pressure hull
oa= overall hp- horsepower
2. PLANNING THE WORK
2.1 Photogrammetry
Object reconstruction consists besides determination of the
geometry of surfaces the determination of surface texture and
colour of the related object, so that we have a complete
description of the object. The surface reconstruction of objects
is today one of the main duties of digital photogrammetry.
Photogrammetry derives the necessary measurements from the
images, rather than measuring them directly. One of the most
important advantages of photogrammetry is to provide
automatic measurement possibilities through image matching
techniques for the collection of the three dimensional
coordinates of the points. After the photogrammetric processes
visualization and computer graphics are needed for the 3D
reconstruction process.
A typical example of photogrammetric surface measurement is
the acquisition of ground surfaces. These surfaces are usually
considered sufficiently well described by the capture of points
in a grid (no discontinuities), other significant points such as
peaks (discontinuities) and lines either as break-lines
(discontinuities) or form-lines (no discontinuities). Area
clements are derived from the captured basic elements "points"
and "lines" by appropriate modelling.( Kraus,K.)
Photogrammetry is very powerful method to generate point
clouds, which will be processed for further processes such as
visualization and graphics techniques.
2.2 Used Camera
In the first step of the project only the digital camera Olympus
Camedia C-4040 with the following characteristic was
available. Images were acquired with this camera.
CAMERA SPECIFICATIONS
* Maximum image resolution: 2272 x 1704
e Maximum CCD resolution: 4.14 megapixel
* CCD size: 2.54/4.57em
* Optical zoom: 3x
* Digital zoom: 2.5x
Shutter speed range: 1 to 1/800 sec
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
* Focus range: 7.1mm-21.3mm
2.3 Used Software
Photomodeller uses photogrammetry to recreate threc-
dimensional models. The user creates a project using Photo
Modeller. Images are added to the project. The user indicates
points on the images with the mouse. To recreate the model
some points must appear in more than image. Next, the user
creates triangles by connecting the previously created points.
The obtained triangles form the surfaces of model.
Photomodeller can save the recreated model in a variety of
formats. ( PhotoModeler Pro)
3. PHOTOGRAMMETRIC PROCESS
3.1 Images
Images were acquired with a Digital Camera using a tripod. 60
images are taken and all of them are used for the evaluation.
The three wreck parts are located at the open part of the
museum and there were trees around them. Therefore, the
measurements are planned to select the best location and the
optimum number of camera positions without being disturbed
by the trees. The brightness and contrast setting are artificially
changed to enhance the images.
3.2 Calibration
The focal length, sensor format size, principal point, and lens
distortion parameters are obtained as the calibration result of
each metric digital camera. The used camera Olympus Camedia
C-4040 has a focus range from 7.1 to 21.3 mm. The calibration
of the camera were performed using the fix focus of f= 7.1 mm.
For this purpose the camera was calibrated on the test field
using the Pictran Software. (Kulur,S.) The Photomodeller
software contains a simple method to obtain the calibration
parameters. The camera was calibrated once according to the
instructions of the Photomodeller User manual. Both
calibration results are compared with each other and an
adequate result has been obtained. The test field used for the
calibration is as shown by Figure 3.
Figure 3. Test field for the calibration process.
