Geoscience Reference
In-Depth Information
scale borders can be linked to the generalised small scale borders. This is
accomplished based on the fact that the topological map of nodes, edges
and polygons of the Administrative Units at the medium scale and those of
the generalised Administrative Units at the same hierarchy level are iso-
morphic graphs (
Figure 5
). Two graphs are considered isomorphic if there
is a one-to-one correspondence between their nodes and their edges. In
other words, the conditions of connectedness and adjacency correspond,
even though shapes may be quite different (Laurini and Thomson 1992).
The application of the “simplification” generalisation operator does not
change the topological map, since the nodes of the lines remain in the
same position. In addition to this, it is the hierarchical level of the codes of
the adjacent Administrative Units that determines the hierarchy level of the
border.
3- Case study and results
3.1 The ESDIN project
The European Commission's ambition to build a European Spatial Data
Infrastructure (ESDI) based on the National Spatial Data Infrastructures in
Member States, for which INSPIRE (Infrastructure for Spatial Information
in Europe) is the legal instrument, is currently in development. ESDIN
(European Spatial Data Infrastructure with a Best Practice Network)
(http://www.esdin.eu/) is EuroGeographics most recent project that fur-
thers this by focusing on helping NMCAs prepare their data for INSPIRE
Annex I themes and improve access to them. One of ESDIN's goal
(ESDIN DOW 2008) is the generalisation of the EuroRegionalMap (ERM)
medium scale (1:250 000) data in order to create the EuroGlobalMap
(EGM) small scale data (1:1000 000) based on rules. Feasibility testing of
the ruled-based generalisation is carried out in a GIS environment.
3.2 Generalisation in the ESDIN framework
A condition-action modeling will be used for the ruled-based generalisation
process in the ESDIN framework. Rules are the result of the comparison
