1. INTRODUCTION
1.1 Motivations and challenges
Numerical cartography can be a widespread planning aid but it
should be provided with defined characteristics to be used for
certain purposes and defined working environment. For this
reason, building and testing numerical cartography, important
features should be pursued in order to prepare the data not only
to be visualized but also and especially to be managed in a GIS
environment for advanced spatial analysis.
Sharing different kinds of information, and among them spatial
data, put the question of construction of a cartographic model to
build and manage geographical information at large, medium and
small scale. So it becomes necessary to solve many problems
concerning the use of different GIS instruments by customers, the
definition of an appropriate format for exchanging and
transferring of geographic data, the design of a common
cartographic model.
It is important to underline that this common cartographic model
should be:
- printable, by means of a defined common graphic style
- arranged for generalization into smaller scales (multi-precision
database handling)
- geometrically exact
- topologically structured with a shareable geometrical and
semantic content. This is indispensable to allow advanced
applications (like route calculation on a graph) and GIS
management.
- interoperable in terms of open data format, metadata and
service interoperability.
In this context the CItyGML format should be of help giving
standard to describe three-dimensional geographical objects in
terms of geometrical, topological and thematic aspects and
making in this way easier to exchange and transfer them from a
drawing/GIS instrument to a different one. Generally every GML
file is combined to a schema file with a structure referring to the
rules defined by Open Geospatial Consortium.
In addition to the above, the three-dimensional content is
nowadays an important information and a must to allow not only
visualization but also geoprocessing and computation (like
volume calculation, visibility charts, cost's evaluation, etc.).