Geography Reference
In-Depth Information
During the creation of the 3D model of the Terez
´
n it was necessary to search for
available information, documents and materials about the situation in the Terez
´
n
Fortresses during the Second World War. There was a need to select proper
information from huge amount of collected materials, which are useable for both
3D geovisualization of the Terez
´
n Fortresses and also for descriptive data about the
life in Terez
´
n ghetto during the 2nd WW. All original archive materials were kept
in four different archives in Czech and Austria. More information about data
mining used in this project can be found in H´jek et al. (
2013
).
With regards to the concept of the virtual model of the Terez´n, the model
consists of two main parts: geometry and related descriptive data. The geometric
part consists of 3D models which capture how the Terez´n ghetto looked like during
the 2nd WW. The descriptive part is based upon structured database of collected
documents (descriptive data) which describe the historic information of many
particular places in Terez´n during the period of interest. For these main parts of
the model have been used two main approaches. A Content Management System
for the descriptive data and a principle called Level of Detail for the geometric
spatial part.
Content Management System (CMS) is a tool for handling, together with
a relational database, all the descriptive data (because historical documents of
varied characters need to be shown such as scans of plans, photographs, books,
etc.). Each document in CMS has not only its own unique identifier, but also an
identifier of a place and time where the document is referred to. For more infor-
mation see chapter
Data storage and interactivity of 3D models
.
As mentioned above, there are a huge number of documents related to events and
places in Terez
´
n. But on the other hand, the spatial part of the model is also
information-rich. Thus there is a need for dealing with this huge amount of spatial
3D data in the sense of quick querying on data, data visualization and serving
relevant data to the user. That
s where the principle of various Levels of Detail
(LOD) is implemented. The principle comes from the CityGML specification (see
OGC
2012
) and it deals with different models for a building, while each model has
its own amount of displayed details of the building and the more detailed model is
built up on the base of the less detailed model. For more information see the next
chapter.
'
Modeling of Buildings of Terez´n Fortresses
Each LOD of a building is stored in a base of data separately. Using different LODs
facilitates so called view-dependent visualization, while the models which intend to
be displayed are chosen based on the position, the view-direction and the distance
of an observer. Each building has a bounding box, abbreviated as BB
(BB
minimum volume that encloses a set of objects or data points), which
represents the building for purposes of selecting appropriate LOD of the building.
The definition of displaying a particular building in a particular level of detail is
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