Coupling Terrain and Building Database Information for Ray-Tracing Applications

In this paper a methodology for the combination and integration into a single data base of terrain and building data is presented. This study is justified if ray-tracing techniques are to be used in propagation and channel modeling studies. Usually terrain is available in grid or elevation form while building information is normally facet-oriented. Ray-tracing (RT) techniques deal with flat facets and straight edges, if possible in triangular format. To allow the use of RT on urban areas over irregular terrain a common format made up of facets and edges is therefore needed. In this article, the procedure to accomplish this data homogeneity is presented. It is assumed that terrain data is available in two formats: a) grid elevation and b) contour or iso-altitude lines. Building data is assumed available in plant, polygonal planar contour form, a primitive and yet widely used format which is yet to be transformed into 3D entities. The geometric modeling of joint terrain and building data is further difficuledt because union of surface objects (even after achieving a unified format) is undefined from the point of view of 3D boolean operations.