Documentation of the Palmyrene Tower-Tombs in Syria ... 
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A 3D-object in VRML is described by different nodes. There are nodes for geometry and appearance. While appearance-nodes 
consist ot material (standard surfaces) and image-/videotextures (advanced surfaces), geometry-nodes may be represented by 
spheres, boxes, cylinders, cones (standard shapes) or different grid layouts , e.g. rectangle-grids. For the detailed visualization of an 
irregular surface like those of the Palmyrene tower-tombs VRML supports with the nodes IndexedFaceSet and IndexedLineSet types 
of polygonal grids. While IndexedLineSet-node is responsible for line connections, IndexedFaceSet-node is used for placing surface 
objects as textures. Using these nodes one can recreate surfaces through converting measured object coordinates into VRML 
coordinates. So it is possible to adapt the distance between the nodes to the needed accuracy. Both, IndexedLineSet and 
IndexedF aceSet are sub-nodes ot geometry-node. Attributes of visualized objects must be defined in appearance-node. These 
attributes are, for instance, the color of surrounding lines and the bitmap file(s) containing ortho-image information. However, which 
parts of image the VRML browser has to cut off and map onto the surface of the model must be declared in a texCoord-node (a sub 
node of a IndexedFaceSet-node). This is important because an ordinary bitmap possesses a rectangular shape and in most cases 
would not fit the model boundaries. 
Although the theory behind of all these steps is not very difficult, the practical application was not that easy because of poor software 
support. Manual editing was required for most of the model parts. In this work, the overall cost was still manageable, but for larger 
projects the manual way of constructing object models is not feasible. Providers of photogrammetric software solutions should think 
about interfaces for semi-automatic, interactive creation of VRML 3D-models. Making results of archaeological photogrammetric 
campaigns visible to everybody can give considerable benefits for research and education. Furthermore, a visualization can help to 
convey much more information than any other form of documentation [Stamm, 2001]. Figure 4 shows a screenshot of 
thevisualization of the Elahbel tower-tomb in an Internet Browser equipped with CosmoPlayer 2.1 (Silicon Graphics, Inc.). The 3D- 
model can be moved, rotated and scaled and enables the user to discover the object from all sides. 
5. CONCLUSION 
Photogrammetry offers powerful tools for documentation and visualization and is hence suitable for interdisciplinary archaeological 
projects. However, it is indispensable that both photogrammetrists and archaeologists share their expertise. As a result of the 
presented project it can be concluded that using photogrammetric software still needs special knowledge and experience, especially 
given the peculiarities of terrestrial applications and the fact that only specialized software packages take them into account. The 
same can be stated from an archaeological point of view regarding the interpretation during stereoplotting, where profound 
archaeological knowledge is needed. 
Although the presented methods for image capturing reveal that analog techniques are still very useful, it must be stated that image 
capturing will be predominantly digital in the near future, especially in terrestrial applications. A digital camera should have a fixed 
focus and should be calibrated in advance. If the camera is equipped with a zoom it must be assured that the zoom can be locked at a 
specific position. Compared to conventional photography, digital image capturing is almost only limited by spatial resolution. 
A big potential lies in 3D-visualization, but more user friendly software packages are needed to make 3D object modeling easier. The 
actual project showed that mapping of textures on 3D-objects is possible and yields good results. 
ACKNOWLEDGEMENTS 
The project was financially supported by the German Archaeological Institute, Damaskus, Syria (Deutsches Archäologisches Institut, 
DAI) and the Hegeman Foundation, Technical University Berlin, Germany. Without this help the project could not have been 
realized. 
Surveying instruments, photogrammetric equipment and software were provided by the Technical University Berlin (TUB) and the 
Technical University Munich (TUM). The academic support of Jörg Albertz (TUB), Klaus S. Freyberger (DAI), Lothar Griindig 
(TUB) and Manfred Stephani (TUM) is greatly acknowledged. Thanks also to Jana Krüger for the helpful contribution during field 
surveys. 
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