Exploring 3D models for geospatial data management: an application of TEN model

Today, GIS software allows 2D representation of real world; 3D representation is limited usually to elevation, surface and contour data. This kind of representation requires often a drastic simplification of real world elements to be described. Common GIS software support 2D topology, 3D elements geometric description, but no 3D topology is allowed; when is necessary to manage 3D topology it is required to use specialized add on tools. In the last years many 3D geospatial models have been proposed. Few of these models are actually applied in the current practice. Usually, in GIS, the model used to describe objects is unique and it is a surface model. Some recent GIS software today allows add for some element a description volume based (voxel). Suitable models for planning could be surface element models, while a volume based model could be more suitable for terrain description in order to carry out terrain analyses. Actually, two ways could exist in order to obtain a global model useful to perform different kinds of calculation according to the characteristics of each class of real world objects: -a first one in which the model is composed by surface and volume object; this mixed model could anyway results too complex to manage; -a second one in which the model is composed only by surface objects which could be derived from the boundary of a TEN model or part of it (e.g. for terrain blocks); so the objects for which could be required a triangular discretization, to perform whatever possible calculations, might be easily converted from surface to volume model and vice versa. This last one could be the right strategy to manage geospatial real world information, on which the work here described has been developed. So this paper reports experimentation on tetrahedral model, chosen among those investigated because well-suited to perform processing related to the global behavior of some real world elements such as the soil, dealing also with possible transformations of volume element description to surface element model.