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.

Table 1. WallMan can handle two-dimensional databases as well as three-dimensional ones.
  Indoor Database Urban Database

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.