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A display encapsulates a coordinate system and the
knowledge of how to place objects onto a portion of the
physical computer screen. À graphic tool is and objects
that "knows" how to draw a GO on a display with a
certain set of symbols. CGen interferes with the process
of cartographic representation two times. First time,
CGen enables it to restore the generalized image of GO
in the required level of details depending on entity
characteristics as prescribed in the multi-detail model.
During the next stage CGen solves conflicts: geometrical
(too small, too narrow, too short, too close) (Mackaness,
1994) and semantic, which are based on the nature of an
entity and links between entities (e.g., a road crosses a
river, the latter being over 2 m deep; here a third entity
must be shown - a bridge). During such conflicts solving
interference of an operator can be needed, so an
exchange of messages between CGen and the user's
display is required.
GO topology of two types can be supported: local
neighborhood topology and Delaunay triangulation.
Support of base topology and creation of "on flight"
topology for intermittent detail level can be useful while
solving conflicts at visualization of cartographic images
of entities and control of adequacy of CG processes.
CONCLUSION
The representation methods of various generalization
techniques of multi-detailed objects, the results of the
inventory of existing guidelines of Russian cartography,
the operation and corresponding map generalization
techniques were investigated in early works
(Govorov, 1994,1995, Khorev,1996). Also, CG methods
for the 1st and 2nd levels MGISs have been identified
and systematized.
The defined objects of MGIS can be used as: 1)
functions for object-oriented model of features; 2)
principles for construction multi-detailed structures of
the features or geometrical objects; 3) selection
techniques of suitable algorithms for cartographic
generalization.
It must be noted that the proposed approach to creation
of MGIS and the developed complex of software, has as
its prerequisite the ability to re-construct and interchange
components of the system. Also for realization of MGIS it
is proposed to use such modern technologies as OLE
and DDE data exchange.
To make up the full package of the system it is proposed
to use the GO library sets for various theme applications,
including industrial DMS and CG.
Further research efforts will be concerned with
development of spatial access mechanism by means of
the overlapping region's scheme; the questions of
integrity of multi-detail representation data base;
methods of maintenance of topological objects
relationships; object-layer organization and linking; tiling
and edge-matching solutions.
The proposed approach is taken as the main principle for
development of an object-oriented — geographic
information system "SOCRAT-GEO". The "SOCRAT-
GEO" uses BORLAND C++ 4.51 compiler, tool kit for
Creating a "client-server" application - DELPHI95, and
other programming tools.
449
ACKNOWLEDGMENT
The authors should like to express theirs appreciation to
the Russian Foundation of Fundamental Research which
have provided partial financial support for the research.
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