3. SURFACE AND PROJECTION 
To proof the feasibility of this approach we have applied it 
to several objects. Some have been architectural, 
archaeological and even some others forensic projects. 
The practical work has to be done in three stages: The 
first is to get both, the external and internal orientation of 
the camera and the detailed 3D-model of the object's 
surface. The second stage completes the missing (e.g. 
hidden) features within a CAD program, the third stage is 
projecting the images onto the object's surfaces by using 
a "digital projector”. 
  
digital or analog camera 
(data acquisition) 
  
bundle adjustment 
(point cloud and orientation) 
  
  
CAD system 
(lines & surfaces) 
  
3D rendering 
(digital projection) 
"digital slide”. Every spot light projects on those parts of 
the object only which had been selected by the criteria of 
the best angle of intersection and its visibility to the 
particular surface. The other surfaces will be projected by 
any of the other digital projectors. 
Before using an image for projection, an enhancement 
has to be performed for these images to adjust their 
radiometric levels to each other. Some other 
improvement has to be done brightening shadows in 
some of the images and erasing reseau crosses or other 
disturbing parts. 
  
scanner, Photo-CD 
(if analog film used) 
  
image enhancement 
(preparation for mapping) 
VTR, Photo-CD, 
printer, plotter ... 
Figure 1: Data flow scheme of the approach 
We used a common bundle adjustment software to 
determine the external and internal orientation for each 
camera station and the object points’ space coordinates 
which have been selected on the object's edges and 
surface representing the border lines and faces of the 
different parts of the object. 
The 3D-model for the object has been edited and 
completed. Hidden parts have been reconstructed and 
surfaces have been defined. At least holes in the 
projection surface have been closed, all that using a 
common CAD program. Rendering the object proofed the 
completeness of the model's surface. 
Figure 2 shows this process with the results of the 
described steps of creating the projection surface. 
To get a virtual model of the object's reality with all its fine 
details, a spot light, the so called "digital projector”, has 
been used to map the images onto the object's surface. 
These projectors shine from the camera’s positions and 
with the same focal length and twist angle through a 
216 
4. TEST PROJECTS 
Two projects have been chosen to show the results of the 
approach. The first one is the test project "Otto-Wagner- 
Pavillion Karlsplatz Vienna” (Waldhäusl, 1991) which has 
been adopted by the International Committee for 
Architectural Photogrammertry (CIPA) for testing the 
accuracy of non-metric cameras for monitoring the 
world's architectural heritage. 13 small format images 
have been transferred to Kodak Photo CD (Hanke, 1995) 
and were orientated by bundle adjustment using self 
calibration. The 3D model of the object has been created 
in the same way. About 1000 detail (mostly plain and 
cylindrical) faces describe the facades of the impressive 
Karlsplatz object. The digital projection is done using 7 of 
the original images covering all of the surface with its 
texture. 
One of the most important results are orthoimages for 
each facade containing all of the details of the object. 
Figure 3 shows one of the orthomaps of the Karlsplatz 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996 
  
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