The source data for a site model is the 3D information used to create a representation of the existing site. The information can be in the form of 3D loci, 3D polygons, or surveyor data. The site model object created from the source data contains both 2D and 3D site information, and it can be copied to other layers and files. Special “snapshot” copies of the site model allow different forms of site model to be shown side by side.
When the site model is generated, two forms of the digital terrain model (DTM) are created and can be displayed—the existing DTM and the proposed DTM. The existing DTM is a direct representation of the source data. The proposed DTM is the existing DTM, plus the geometric effects of site modifiers, such as roads and pads. The existing and proposed DTM can be displayed or hidden at creation or from the Object Info palette.
Site models use the Triangulated Irregular Network (TIN) method to connect input data. This method can work with data that are scattered and in clumps—they do not have to be organized in a rectangular grid. The model uses all the data, without doing approximations, to create a network of triangles. These triangles form the terrain model; the model then performs interpolation to calculate the threading of contour lines.