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ЯНЯЯШШМИШ! 
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
3.2 i3D technology 
In the virtual globe technology i3D, developed at the University 
of Applied Sciences Northwestern Switzerland (FHNW), we try 
to address the above-mentioned shortcomings by supporting 
and integrating imagery data and arbitrary geosensor data in 
real- or near real-time. In the development we aim at integrating 
geosensor data at a sub-meter accuracy level. In Figure 2 a 
screenshot of the i3D virtual globe is presented. 
, 
Figure 2: Print screen showing the virtual globe editor and 
viewer i3D Studio with a scene of Europe 
Subsequently, the i3D technology and its main components are 
introduced. Thereafter, the i3D video data integration module is 
presented in detail in the main part of this paper. All 
components are part of the i3D Studio software system. 
3.2.1 i3D core 
i3D is a 3D geovisualisation engine which is optimised for real 
time spherical rendering of the entire globe. Like other virtual 
globes i3D can also stream extremely large volumes of geodata 
over networks or from local drives. Supported geospatial 
content types are digital terrain models, orthomosaics, points of 
interest, and 3D objects. i3D uses an extensible scene graph 
concept to define a virtual world scene. This scene graph can be 
custom-built for arbitrary application scenarios. For application 
development and customisation a scripting API is available 
based on the high performance lua scripting language 
(Ierusalimschy, 2006). 
The i3D virtual globe is based on an ellipsoidal earth model. As 
position reference the ECEF WGS84 reference system is used 
and the geoid is defined as height reference surface. This 
definition is important when a GPS-based geosensor 3D 
position has to be integrated into the virtual globe. In case of a 
geoidal reference surface as in i3D, this GPS height has to be 
corrected with the corresponding geoid separation. 
3.2.2 i3D collaboration framework 
The i3D collaboration framework enables the creation of a 
collaborative virtual world (Nebiker et al., 2007). In this 
environment, it is possible to visualise and exchange 
information between different collaboration clients. In i3D, this 
information could consist of the position and attitude of an actor 
(virtual camera) located in the virtual globe or of an arbitrary 
geoobject such as a point of interest. Furthermore, this 
framework allows the integration and utilisation of distributed 
geosensor data in real-time. 
4. VIDEO DATA INTEGRATION 
In the following the developed video imagery integration 
processing chain and software components are described, which 
enable the realisation of real-time and offline augmented 
monitoring and virtual monitoring solutions based on mini and 
micro UAV systems on the one hand and the i3D virtual globe 
technology on the other. In this context the term augmented 
monitoring refers to the superimposition of the geo-registered 
video stream with objects of the virtual globe. In contrast to this, 
the virtual monitoring approach refers to the synchronised 
rendering of the video stream in parallel to the virtual scene 
containing the UAV system and the geo-registered view 
frustum of the video camera. Figure 3 shows an example of the 
augmented monitoring scenario with an overlay of the semi 
transparent video in the centre of the screen with the 3D 
scenery of the virtual globe. Figure 4 depicts the virtual 
monitoring video imagery integration approach presented, with 
the video view of the real world on the left hand side and the 
synchronised virtual view on the right. 
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Figure 3: Example of the augmented monitoring scenario 
Figure 4: Example of the virtual monitoring scenario 
4.1 Systems architecture and data flow 
Figure 5 shows all involved hardware components and the 
entire data processing chain of the developed prototype solution. 
At the beginning of the chain is the mini- or micro UAV 
platform consisting of a flight controller, a video camera and a 
data link transmitter. This video camera captures the imagery 
stream that will be integrated into the virtual world. With the 
deployed 'microdrones md4-200' platform an analogue data link