Indoor and Urban Vector Databases
If the area is not very large and if the number of buildings is small, also indoor databases can be used to model an urban environment. Indoor and urban databases are similar – except for the orientation of the objects. In urban databases, the basic element is a polygonal cylinder which is built with many planar objects. Only the roof of the cylinder is defined and used. All walls are generated during the propagation analysis when they are needed. They consist always of four corners and are vertical. This limitation of the data format saves a lot of memory and is therefore very efficient for large databases with several thousands of buildings.
In indoor databases the orientation of objects is arbitrary - this is the basic difference to the urban databases. To model a simple building with four walls and a flat roof, five objects are needed and each object has four corners. Therefore, indoor databases are limited to smaller areas with fewer objects. But the environment can be as arbitrary as possible – ranging from a small campus down to a single room.
| Indoor Database | Urban Database | |
|---|---|---|
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| Basic element | Planar wall with polygonal shape | Polygonal cylinder with uniform height |
| Object definition | By corners | By shape and height |
| Object orientation | Arbitrary | Vertical to ground |
| Number of corners | Arbitrary (limited to 256 for some propagation models) | Arbitrary (limited to 256 for some propagation models) |
| Material | Individual for each wall | Individual for each building |
| Additional objects | Subdivisions like doors and windows | Vegetation and virtual buildings |
A 2D indoor database consists of one floor with all walls vertical and in the same height. Opposed to that a 3D indoor database can have objects with an arbitrary height and orientation.
Similar to that 2D outdoor databases contain buildings with equal heights and 3D outdoor databases contain buildings with different heights.