Abstract
3D city models are widely used in many disciplines and applications, such as urban planning, disaster management, and environmental simulation. Usually, the terrain and embedded objects like buildings are taken into consideration. A consistent model integrating these elements is vital for GIS analysis, especially if the geometry is accompanied by the topological relations between neighboring objects. Such a model allows for more efficient and errorless analysis. The memory consumption is another crucial aspect when the wide area of a city is considered – light models are highly desirable. Three methods of the terrain representation using the geometrical–topological data structure – the dual half-edge – are proposed in this article. The integration of buildings and other structures like bridges with the terrain is also presented.
Highlights
GIS as it was originally envisaged was largely concerned with the polygon-based description of the land (1)
It was not long before graphics systems started “planting” simple building models on the landscape: examples of this are available from various commercial vendors
A geometrical-topological model proposed in this paper for building and terrain representation is based on a simple idea – it consists of edges and nodes; edges bounded by nodes and linked together form a cell; several cells are connected into a cell complex by edges, but in the dual space
Summary
GIS as it was originally envisaged was largely concerned with the polygon-based description of the land (1). A geometrical-topological model proposed in this paper for building and terrain representation is based on a simple idea – it consists of edges and nodes; edges bounded by nodes and linked together form a cell; several cells are connected into a cell complex by edges, but in the dual space. The resulting model consists of building internal and external cells linked with the terrain model – in the example shown in Figure 7(a)) the building is represented as a simple block. In 2D+3D model the connector detection may be done by checking the flag (introduced in the previous section) or by adding and testing a special attribute at the dual node representing the connector cell
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