Historically, terrain information has been represented and visualized as couture lines, i.e. lines connecting points with identical elevation values. This was primary because of the way this information was collected, first through field mapping and later through stereoscopic Stereoscopic photogrammetry. While couture lines are still used for terrain visualisation on many maps, they are unsuitable for digital representation aimed at 3d visualisation and modelling. For these purposes, a raster representation-based representation or a 2.5D Triangulation model [TIN model]
Representation of Buildings and Tunnels
There are several problems in relation to the representation of bridges and tunnels namely: