Basic Elements: Cylinders with Polygonal Ground Plane

Urban vector databases contain a description of all buildings and vegetation areas in an urban environment. The buildings are described by polygonal cylinders, buildings with arbitrary shapes can be used. The building database offers the following features:

• Each polygon can have an arbitrary number of corners (for some propagation models this is limited to a maximum of 256 corners).
• At least 3 corners are required to define a valid polygon (building).
• Each building has a uniform height (polygonal cylinder). The height is either relative to the ground or absolute above sea level. Absolute height values require additionally a topographical database.
• Flat rooftops are used (horizontal planes).
• Only vertical walls (parallel to the z-axis) are allowed.
• Each building has a single set of material properties which are used for the whole building.
• The polygon of a building must not intersect itself.
• The polygon of a building might intersect other polygons (buildings).

If angular roofs must be modeled, the indoor database format and prediction tools must be used.

Buildings totally inside other buildings are removed because they do not influence the wave propagation at all. If the inner building is taller than the surrounding building it will be kept and considered as.

Up to now, the databases must be in UTM coordinates (meter) and the building ground-planes are therefore defined in an orthogonal 2D coordinate system (x is longitude, y is latitude).

The topography itself is not included in the vector database of the buildings (only the height values can be absolute above sea level – but no additional data about topography is included). But an arbitrary topographical database can be considered.