First steps towards formalizing generalization operators a topdown approach

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First steps towards formalizing generalization operators a topdown approach

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Role of symbolization. Exclude symbolization from the cartographic generalization process ... is always applied on symbolized (cartographic) features ... –

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Title: First steps towards formalizing generalization operators a topdown approach

1
First steps towards formalizing generalization
operators -a top-down approach

Theodor Foerster
13 July 2007, ifgi, Muenster

2
Overview

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

3
Introduction

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Generalization
The adaptation of geo-data according to user and
use requirements
Model generalization (? data)
Cartographic generalization (? maps)
Generalization process consists of different
generalization operators

4
Generalization operators

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Provide an abstract description of generalization
functionality
Important to abstract human knowledge
Allows comparing generalization functionality
An operator is implemented by different
algorithms
Operators are not interfaces!

5
Motivation

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Different classifications are available
Do not cover all aspects
Project-driven
Not formal
Classification is important
For enabling automated web-based generalization
processing
Transparency for evaluation
Knowledge exchange
Producing on-the-fly base maps for different
scenarios on the Web
RGI 002 DURP ondergronden project
(www.durpondergronden.nl)

6
Gruenreich model

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Reality
Object generalization
Model generalization
Primary model
Cartographic generalization
Cartographic model
Inspired by Gruenreich (1992), ATKIS - a
topographic information system as a basis for GIS
and digital cartography in Germany
7
Classification framework

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

8
Model vs. cartographic generalization operators

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Model generalization operators can be defined on
feature type level
Cartographic generalization operators are defined
on feature instance level
Both are applied on feature instance level!

9
Operator classification

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Identified operators are based on literature

10
ISO 19109

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

11
Model generalization operators

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Class Selection
Reclassification
Collapse
Combine
Simplification
Amalgamation

12
Collapse Combine

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Changing the geometry type
Collapse
Decrease dimensionality
Example Collapse road polygons to road lines
Combine
Increase dimensionality
Goes along with reclassification
Example Combine leisure sites (modeled as
points) to touristic attraction (modeled as
polygon)

13
Simplification Amalgamation

Introduction motivation
Classification framework
Model generalization operators
Cartographic generalization operators
Outlook
Current questions

Simplification
Mainly used for data reduction
Deletes aspects of the feature
Not that invasive
Amalgamation
Amalgamating a group of features to a new feature
of same geometry type
Goes along (mostly) with reclassification
Example Merging adjacent polygons of different
types of forest to a new feature of type forest.

14
Role of symbolization