ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
GENERALIZATION FOR 3D GIS
Fengwen BAI, Xiaoyong CHEN*
Space Technology Applications and Research Program
School of Advanced Technologies, Asian Institute of Technology
p.O. Box 4, Klongluang, Pathumthani 12120, Thailand
E_mail: fwbai64@yahoo.com, xychen@ait.ac.th
KEYWORDS: Generalization, 3D, GIS
ABSTRACT
The development of Geographic Information System (GIS) has inputted new vitality for the map that has been used thousands of years
as the widespread and common tool for academic and reference object. 3D GIS as the characteristic of visualization of the reality is
more and more becoming an indispensable component of future's GIS thought automated generalization in 2D digital map/GIS is still
the outstanding question. The future availability of automatic generalization tools has allowed us to realize our goal, namely the
generalization in 3D GIS, will be the basic research in the field. The paper which is focused on the theoretical research for 3D GIS
based on the characteristics of 3D GIS explores several different ways for generalization associated with simple examples: a) Levels of
systems which displays different detail elements comparing to the area or scale from large scale 3D GIS to small one; b) Symbolization
in both small and large scale 3D GIS, including the design of symbol; c) Refinement such as selection, aggregation and simplification
etc. of features are used to generalize features according to the functions and area characteristics. Those will provide an explorative
approach to the 3D GIS production in normalization and comparability to each other. Some basic algorithms and operators have been
expanded from 2D GIS to 3D GIS.
INTRODUCTION
Traditional maps displaying the Earth in 2D have been used
thousands of years. Human beings had been not realized their
dream of displaying the real world as it is in 3D and more until
the invention of computer. The mapping industry has taken the
revolutionary move of replacing 2D, traditional manual work by
3D and computer-driven processes. Generalization, the art
and theory with which cartographer describes the world by
selecting and drawing elements on the map, has been
developed at high level in 2D mapping (It does not overstate
that a cartographer is an artist). Semi-automated and
automated generalization theories have been developed and
used in variable of mapmaking.
Geographic Information System (GIS) that serves long-term,
multiple-purpose applications has become a hot industry in the
recent decades. GIS is as a tool that captures, stores,
manages, manipulates, analyzes, models and displays
information with respect to geographic space. It is the rapidly
growing information technology area at today’s information
age.
Generalization is the simplification of observable spatial
variation to allow its representation on the map (Goodchild,
1991). It is an information-oriented process intended to
universalize the content of a spatial database for what is of
interest (Muller, 1991). Relating observation of geographic
space to models of geographic phenomena converts data to
knowledge, Once a model of the phenomenon has been
developed, it is possible to generalize that model. Cartographic
generalization may be considered to be an exercise in applied
geography (Pannekoek 1962); for example, generalization of
contours, coastlines, streams, and topographic surfaces
should incorporate knowledge of landforms and geomorphic
process. Furthermore, the cartographic character of many
features is scale-dependent (Buttenfield 1989), and the use of
a single database to support mapping at a variety of scale
presents many research challenged (Beard 1987).
Generalization in 3D GIS will become an indispensable
component of future's GIS. Whatever the task, compiling data
in different sources into a master database to compose an
output from it for data compression, analysis, or
representation, generalization is most likely involved.
Map generalization. One of the greatest challenges to
cartographers working with digital systems has been
automating the map generalization process (Robert, W 1999).
Manual generalization, as the traditional means, is extremely
subjective and time consuming. Cartographers draw a reduced
map by hand. They eliminate unimportant features, simplify
lines and boundaries, combine area features, and resolve
conflicts as they draw. The result is, no doubt, operator-
dependent. As geographical databases are constantly built,
the request for automation of generalization capability for
multi-purpose output is in demand. The field of generalization
has extended to include 3D GIS applications. Noticeable
efforts have been made by researchers and some
GIS/mapping software vendors defined digital generalization
problems and developed solutions. However, none of the
existing 2D GIS/mapping systems has provided a set of tools
that fully satisfies digital generalization needs. Aspects as
automation of generalization are still open problems.
The age movement forward is carried by both the existing
problems solved and new matters found. The future availability
of automatic generalization tools has allowed us to realize our
goal, namely the generalization for 3D GIS, will be the basic
research in the field.
For the main topic of the paper, there are two niches in the
research and market.
• In Research
Up to new, a set of complete theories of generalization in
traditional map had been created and these theories have
been transplanted to the digital map and 2D GIS. Automation
or semi-automation of generalization in digital map and 2D GIS
has being developed based on these basic theories even there
are still some open problems needing to be found. 3D GIS as
the new baby generated with the computer development will
go along the different way: combination the basic theories with
automation. Generalization for 3D GIS would be very valuable
to support the realization of automation.
• In Market
Normalization not only for digital map or 2D GIS but also for
3D GIS is the major question in data product. How to rule a 3D
GIS product is reasonable or not for its data, detail and
selection of elements, etc.? A building, for instance, can be
displayed as a symbol, a sketch with only the walls and the
root or the almost real one that has windows, doors, even the
pattern of the wall. Which one is the better to the user and
which one is fair to the investment. The research can be a
Supported by Visiting Scholar Foundation of Keb Lab. In Wuhan University, P. R. China
