Symbolisation of 3D city models for online visualisation

3D city building models can improve many applications such as urban planning, navigation, disaster management, traffic control etc., in various aspects especially in visualisation. However, compared with the data volume and complexity of 3D city models, the capability of devices and network band are still limited. To improve the visualisation efficiency, generalisation of 3D city models is required. For 3D city models, generalisation creates models in lower Levels of Detail (LODs) from higher LODs. In CityGML standard, five LODs are defined from internal building to the overall digital elevation model (DEM) to describe the city objects. Considering the complexity of 3D city models, it is essential to generalise the models automatically. The CityGML is suitable for representation 3D city models since it supports both geometry and semantic information, but it is not designed and optimised for visualisation. Therefore, X3D is employed for 3D city model visualisation. In X3D, we can define 3D objects and reuse them after translation to represent other object. In this paper, the 3D building models in CityGML are symbolised for more efficient visualisation with X3D. The rest of paper is organised as follows. Related work is introduced in Section 2. Section 3 describes the proposed generalisation methods for different levels. Section 4 presents the experimental results and Section 5 concludes the whole paper.