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TopVisualization of three dimensional (3D) objects becomes more widespread in developments (see Behley, and Steinhage, (2009), Jin and Bian (2006) and Liu, and Fang (2009)). This can be seen from the demand in 3 D based applications (see Freitas, Sousa, and Coelho (2010) and Zhang, Fang, and Jing (2009)). Visualization of 3D objects can support a more realistic view as in the real environment than the two-dimensional (2 D) visualization. 3D view of a building model is more realistic compared to 2D floor plan of a building in a navigation application.
In commercial software development, private companies are competing in developing tools that are capable of managing 3D cities. ESRI (CityEngine), Bentley (Bentley’s Map V8i) and Google (Google Earth) offer users the capability to create, visualize and measure 3D cities in their products (Jazayeri, 2012).
Since quite a number of 3D city model formats are available, there is a need for standardizing the 3D city model format for various applications. City Geography Markup Language (CityGML) is an example of an exchange standard format for 3D city models (see Figure 1). It consists of different Levels of Details (LOD); LOD0, LOD1, LOD2 and LOD3. Different LODs reflect different 3 D spatial information details. The higher the LoD, more object detail and geometry is included. This common information model is the first standard related to 3D city models (Jazayeri, 2012).
Figure 1. LoD2 building illustration: CityGML feature structure as UML instance diagram (taken from Gro¨ger, and Plu¨mer (2012))