A COMBINED AUTOMATED GENERALIZA TION MODEL 
OF SPATIAL ACTIVE OBJECTS 
J. Joubran Abu Daoud, Y. Doytsher 
Faculty of Civil and Environmental Engineering 
Department of Transportation and Geo-Information Engineering 
Technion- Israel Institute of Technology, 32000 Haifa, Israel 
(jacquele, doytsher) @tx.technion.ac.il 
Commission IV, WG IV/3 
KEY WORDS: Generalization, Cartography, GIS, Automation, Analysis, Data Mining, 
ABSTRACT: 
Automating the map generalization process has traditionally been a major focus of research in cartography and 
GIS environment. Many algorithms and models have been developed over the past three decades, starting with the 
line simplification algorithms and ending with "Clarity" the new environment employing AGENTS, JAVA, XML 
and Topology. Although automation of cartographic generalization has been a field of extensive research, a 
method of usable holistic understanding generalization is still lacking. The model for combined generalization 
described in this paper, is intended to initiate a method that understands and describes the action and behaviour of 
active objects in the map generalization process. The paper focuses on the object properties analysis in order to 
determine the "power" of each object in any given map. and the interactions between these powers. These 
interactions produce "forces" that act on the objects and control their behaviour according to the cartographic 
constraints. 
1. INTRODUCTION 
Cartographic — generalization aims at simplifying the 
representation of cartographic data to suit the scale and purpose 
of the map. Although automation of cartographic generalization 
has been a field of extensive research (Muller et al 1995, Weibel 
& Jones 1998, Richardson & Mackaness 1999, and many 
others), there is still a lack of a usable holistic understanding 
generalization method. Successful implementation of a 
generalization process is supposed to produce a good map that 
satisfies the cartographic requirements, rules and constraints. 
Recently several methods have been developed based on 
constraints and rules definition (Raus & Plazanet 1996, Harrie 
1999, Sester 2000, Raus 2000, Harrie 2003). However, it is 
clear that more research on the definition and the formulation of 
the rules and the constraints to be used is needed. The main 
issue of the generalization process is to determine where the 
conflicts are and how to solve them without creating new 
conflicts. The objects in the map must not be treated in 
isolation. and the combined generalization should model the 
relationship between the objects and the way they affect each 
other. Several authors (Ware & Jones 1998, Sajakoski & 
Kilpelanen 1999, Sester 2000) have already suggested such 
holistic process; however, no solution has been presented for the 
implementation of the complete generalization process in a 
single continuous step. 
The research described in this paper examines behaviour of the 
map objects and the interactions between them in order to 
understand the generalization process. The developed model 
defines several parameters that determine for each object a 
"power" in the map, and set rules to control the mutual 
interaction forces between these powers in order to compromise 
between the constraints and solve the competition between the 
objects on the limited map area at a reduced scale. The 
parameters are dependent on the object properties (area, type, 
stiffness, and shape) on the one hand, and the area properties 
(density, empty area surrounding an object, the map target, and 
the map scale) on the other. Each object acts according to its 
power, computed as a function of its properties and these 
parameters. Interactions between map objects are expressed by 
actions of the forces constructed around the cartographic 
constraints and affected by several parameters depending on the 
properties of the surrounding objects. The combined 
generalization model takes into consideration the surrounding 
objects and defines their properties, such as distance, type, 
density and topology. As a result, the surrounding objects affect 
and cause the “weak” objects to change their shape or place. 
The implementation of this new method requires: (1) 
determination of quantities and thresholds of each parameter, 
(2) definition of the rules and the constraints of each force 
action, and finally (3) translation of the results into one or more 
of the generalization operators - displacement, aggregation, 
selection, and enlargement. 
Due to the limited scope of this article, we will discuss the 
interaction among objects belonging to only one layer, 
buildings. This paper will present the new combined 
generalization method of cartographic generalization, its 
implementation, tests on a real data subset, and the results 
achieved. 
2. CARTOGRAPHIC OBJECTS AND THEIR 
PROPERTIES 
The objects in the map are treated according to their properties, 
their type, and what they represent. The cartographic map 
generalization at a required scale is a process of competition 
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