128
The database of this network is numeric and must be
found and elaborated in a graphic form so as to be the
same as that of the existing cartographic Road
cadastre, which remains linked to the national geodetic
network, with a precision relative to its scale (generally
the scales are large, 1:2000 or 1:1000).
The basic cartographic structure of the Road cadastre
is thus made up of the network of the road axes and the
cadastral maps inserted in the national geodetic
network.
The maximum error that is tolerated depends on the
involved elements and the need that it be the same as a
map, by means of a numeric database plot.
Each road will be qualified by means of a series of
attributes that integrate the simple geometric
information and that are defined in the deign phase of
the G.I.S. project, also based on the nominal scale.
For dual-carriage-ways it is necessary to memorize the
center-line of each carriage-way, in order to have
correct information on the plano-altimetric trend.
It is also necessary that the cartographic production
respects some conditions that are particularly useful for
the finality of the information system.
First of all, the roads that connect and cross built-up
areas must always be extended inside the same, so
that the axes are not continuous.
At the intersection of each road with the outskirts of the
built-up area a node will be identified that will allow the
road to be assigned an attribute of urban or extra-
urban.
Inside the urban areas, with the exception of the case in
which the G.I.S. is specifically orientated for the
maintenance of the road network (survey scale >
1:2000), it is sufficient to show only the fundamental
roads (of the eventual motorways that cross urban
areas), guaranteeing, however, the continuity of the
road network, that is the presence of a connection
between all the roads of the urban area.
The element lists to be memorized in the cartographic
supports of the G.I.S. must be compiled with regard to
the information systems scale. On a large scale
(1:1000-1:2000) certainly some elements (e.g. guard
rail, new jersey, horizontal signs, etc.) can be
excessive and not coherent for the level of detail of
lesser scales. In any case the designer of the G.I.S. will
define the nominal scale for the cartographic
representation and its Information content.
Particular attention should be given to the intersections,
which must always be identified with a network node
and described by an attribute that defines the
characteristics.
For the greater scale, from 1:2000 up, which are ideal
for the realization by G.I.S. aimed essentially at the
problem of maintenance, it is useful to extend the
concept of area also to the roads, normally linear. This
is a significative evolution of the information level of
numeric cartography, which, associated to the road
stretch represented by the attribute “aerial development
”, other than the traditional “linear development”, gives a
further important contribution to the knowledge of the
infrastructure.
Naturally, there must be no solutions of continuity in
correspondence to intersections, bridges, tunnels, or
other works or infrastructures that border the road, such
as buildings, walls, special areas, etc.
In the memorization and representation of the road
network, finally, we must remember that the viability
areas are complementary to the definition of the areas
of the urban districts in the same way as they interface
with the hydrographic network. The representation of
the road network must be in keeping with that of the
hydrographic area and urban areas, in such a way that
the map offers no continuity solutions.
Other than the increase of the specific information level
“communication”, the production of maps should
guarantee complete and detailed information on the
“border conditions” of the road system, by means of the
memorization of all the elements that are useful for the
definition of the interferences and correlations between
the territory and road system.
The territorial elements to be memorized are defined in
the deign phase of G.I.S. and required by the company
who will produce the maps with specially designed
regulations.
It is a good general rule that the memorization takes
place at the same time as the “restitution”, immediately
associating to every recognized element its respective
code.
The elements are generally subdivided, other than for
territorial sectors, in relation to the code system, which
can be divided into the following three groups:
• homogeneous linear elements, represented by a
polygon and identified by means of an alphanumeric
code that defines the type;
• linear elements that border areas having different
characteristics, which can be defined by means of
the composition of the identification codes of the
areas;
• point elements, represented by points or symbols
anchored to points, defined by a code that defines
the type.
The border elements, of course, are those that need a
code that is more articulate and complex, which, on the
other hand, corresponds to a greater information
content.
It is first necessary that the border linear elements are
orientated, in a way that defines the area to the right
and left. Furthermore, the areas must be described from
the topological point of view (e.g. “asphalt surface ”,
“pavement”, ....) and from their spatial collocation (“in a
tunnel”, “on a viaduct”, etc.).
Each area, therefore, will be defined by means of an
alphanumeric code that clearly indicates the typology
and collocation; every border linear element will,
instead, be defined by means of a composite code, with
a pre-established succession, of the two identification
codes of the border areas.
