Definition of the 3D content and geometric level of congruence of numeric cartography

Abstract

The research concerns the study about the 3D contents of digital cartography and the successive migration on GIS platform. We choose to work on different datasets (for example the Milan's 3D cartography at scale 1:1000 in DXF format). The DXF format is less evolved and flexible than GML language. This codify was studied in the first part of the project but the its complexity and the incomplete formal definition get the attention to concentrate more on the geometry and the 3D congruence than on the language. The next step was to evaluate the type of geometric components that let to transfer the necessary information contents to the complete description of the examined object, independently from the chosen representation environment. For example, to correctly define in three dimension one quoted point or a contour line is enough to have a simple geometric primitive with a specified attribute; but this type of information isn't sufficent for objects with complex geometry . We try to define the minimal content of threedimensional information that can be associated with an element to have its complete 3D definition, naturally trying to increase minimally the restitution duties. We begin a systematic operation for recognise the elements that are more useful to generate 3D terrain models like scarps, bridges and canals. For other typologies of elements that are represented in restitution phase, we are defining the geometric components for their complete threedimensional representations with particular attention to the geometric congruence between the elements: the study wants try to define the topological constraints among the elements (like in 2D cartographic representation). Other step is to verify the possibility to use these 3D geometric structures inside GIS and GEO-database platforms and to test the capacity of these systems to manage 3D complex data structures.