nbul 2004 
1s do not 
ch better 
nodel the 
jore than 
has to be 
nologies, 
| plotting 
curvature 
rator will 
often the 
ed in co- 
rmly that 
e used for 
led plans 
'ailable at 
- and the 
'rdingly a 
ested and 
letry was 
nd on the 
iefs — the 
scanning 
a list of 
ometrical 
would be 
16 photos 
lon. The 
nt teams. 
ilable, all 
scheduled 
mentation 
blications 
sen in the 
ation 
oordinate 
ts around 
tal angles 
:t for the 
and self- 
0.5 mm 
achieved. 
| scans of 
vhich was 
ose. The 
y photo 
system. 
a MENSI 
Y about 2 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
mm was chosen. This resulted in 20 observation locations from 
where a total of about 10 million points were recorded in about 
60 hours of scanning time. As long as a scanning range of 5 m 
is not exceeded, the MENSI $25 will achieve a point accuracy 
(standard deviation of spatial location) of better than 1 mm if 
correctly calibrated. 
Because the marble reliefs show very fine details, it was neces- 
sary to use a high precision scanner for their documentation. A 
GOM ATOS II scanner was chosen. This scanner projects 
fringe patterns onto the object and uses two cameras to analyze 
the resulting images. Since high resolution was important, the 
version with a 400 mm base and 35 mm camera lenses was 
selected. In this configuration, the scanner yields about 1.3 
million points in a field of view of 175 mm x 140 mm. Thus, 
twelve scans would cover one relief (not counting numerous 
additional scans which were needed to reduce the hidden areas 
due to occlusions). The raw data for one single relief amounted 
to about 450 — 700 Mbytes. 
The GOM ATOS II was also used to document the five statues 
on top of the cenotaph since their surfaces show very fine detail 
(fig. 2).. 
2.4 Photogrammetric imaging 
A photogrammetric documentation of the whole object was 
carried out by a private surveying company experienced in the 
documentation of cultural heritage. A Zeiss UMK metric 
camera was used. In addition, stereo images were acquired for 
each relief on high resolution b/w film. Also, orthogonal images 
were exposed on color film for later rectification and/or 
texturing. 
  
Fig. 2: Kneeling Maximilian 1. Virtual model from scanned data. 
3. DATA PROCESSING FOR SCANNED DATA 
3.1 Merging and thinning 
Data processing which kept one person busy for nearly one year 
was a very delicate task. The procedure which was 
accomplished using Raindrop Geomagic Studio software has 
been described earlier (Bochler et al. 2003). Before the objects 
can be treated, neighboring point clouds have to be merged into 
one data set. The following point thinning process has to reduce 
the data for easier handling without a degradation of object 
resolution. In smooth surface areas, a considerable reduction 
can be achieved, whereas detailed object parts (as they are 
typical for the reliefs) should not be thinned out at all. Even 
with the most advanced hardware and software, one complete 
relief plate could not be treated at the same time without loss of 
detail. Consequently, several partial models had to be created. 
3.2 Meshing, checking manifold meshes, cleaning and hole 
filling 
The following data processing steps include a check for 
manifold meshes which are unavoidable where hidden parts of 
the surface cannot be observed from any point, and a cleaning 
procedure which readjusts neighboring triangles which show 
large orientation differences. A hole filling process completes 
the data processing. 
4. RESULTS 
Presently, the results of our cenotaph documentation belong to 
the most detailed virtual models of art worldwide. The model in 
its highest resolution consists of more than 1.000.000.000 
triangles. It should be noted that this number does not express 
the amount of data collected (which is much larger) but the 
necessary data to describe the object with the desired resolution. 
Because of restrictions in the hard- and software presently 
available, the high resolution model has to be processed and 
stored in more than 140 separate virtual models. Various other 
models with a reduced number of triangles are available for 
visualization and publication (e.g. figs. 1, 2 and 3 of this 
publication).