CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
one. It is important to note that the rectification area can be
chosen larger than the defined plane. The desired number of
pixels per unit length of the end-product are marked in the
equalisation settings. In this study, 1 pixel is taken as 0.01 m.
Finally, the rectified images are saved as BMP file. A series of
sub-pieces of the rectification can be saved to provide ease in
latter colleague work in photoshop. These rectified images are
opened in photoshop and perspective correction is made. The
image size is re-determined according to the desired scale at the
end. In this project, the scale is determined as 1 / 200. Then, the
ratio of the present image size and the measured distance in
rectified photoshop image is proportioned with the ratio of the
new image size and the measured distance in autocad model.
The total size of the overview ortho-photo is calculated as
around 8000 pixels x 700 pixels.
For the detail ortho-photo of the left corner (1/25 scale), two
images were used. The two pilasters, wall piece with window
openings, three different bases and the flat piece at the bottom
of the entablature were regarded as separate planes. The above
described process was repeated (Figure 6).
6.2 Production of Textured 3D Model
In Defensionskaserne, Photo 3D (software for 3D model with
texture from photo) was used for rectification process. Image
library of the digital camera was sufficient for the work. As
stated in section 3.2.2, each digital image covered an area
between two pilasters (6,5 x 14m). ‘File’ on the toolbar was
clicked. An image was loaded by clicking ‘add photo’. Then,
calibration option was selected. Two axes were decided to be
used in the calibration. Therefore, the y axis was hidden.
Two sets of parallel lines making up the borders of the top and
bottom sides of the wall piece with openings, and exterior sides
of the two columns were marked by pulling around the
calibration lines to these defined positions. Then, model option
was clicked on the toolbar. A cursor was initialised again by
clicking the "init" button on the toolbar. This cursor was
streched and moved to one of the planes to be rectified. Then,
rectangle option was clicked on the toolbar to indicate that the
plane definition can be saved. The initilisation process was
repeated for al the planes selected for rectification. Finally,
texture on the toolbar was clicked to illustrate the areas desired
to be used in texture mapping; these are the interiors of the
defined rectangles (Figure 5). Finally, the file is exported as
VRML 2.0 document to a folder and saved.
After the production of the textures, they are sticked on the 3D
model in Autocad environment.
Figure 5. Selection of a plane for texture maping.
Figure 6. Orthophoto of the east elevation’s left corner.
7. CONCLUSION
The application of multi-image measurement and single image
rectification techniques has provided the accurate
documentation of the geometry and texture map of the east
elevation of Defensionskaserne. Three parted working
technique developed for the extraordinary long elevation has
been successful during multi-image measurement. With the
photogrammetric data, 3D textured model of the object has been
produced.
The significance of this end-product from the view point of
architectural heritage conservation is as follows: The 3D model
documents accurately the object. This is an indispensable data
for an architectural conservation project. The textured map is
necessary for visualization of analytical information such as
material types, structural problems, alterations, etc. Therefore,
the combination of the two photogrammetric techniques has
provided an accurate base for conservation studies.
REFERENCES
Atkinson, K.B., 1996. Close Range Photogrammetry and
Machine Vision, Whittles Publishing, Bristol.
Grussenmeyer, P., Hanke, K. and Streilen, A., 2002. Chapter in
Digital Photogrammetry, Architectural Photogrammetry, ed.
by: M. Kasser and Y. Egels, Taylor and Francis, pp.300-339.
