lecture 08 generalization

8/9/2019 Lecture 08 Generalization

1/28

Principles ofCartography (SUG242)

Lecture 8 :

Generalization

Department of Surveying Science and GeomaticsFaculty of Architecture, Planning, and SurveyingUniversitiTeknologi MARA, Perlis


2/28

Knowledge & Theory of Cartography

History

Principles on

Cartography

Map &Cartographic

Process

Geometry Aspect of Cartography

Cartography information sources

Generalization Process

Map Compilation and Design

Map Symbolization

Map Color and Typography

Data Capture and PreparationMap Making and Production

Map Making Management

Lecture Outline & Strategy for SUG 242


3/28

Outline For Todays Lecture.

1. Generalization Concept

2. Elements of Generalization

3. Controls of Generalization


4/28

What is generalization?

y Generalization is the process of reducing the informationcontent of maps due to scale change, map purpose,

intended audience, and/or technical constraints.

Why we need generalization in mapping?

y Real world is too complex, maps cannot retail all the

information in the real world, therefore we need to

simplify the reality.


5/28

1) reduce complexity2) retain hierarchy

3)maintain spatial accuracy (e.g. shifting)

4)maintain attribute accuracy (e.g. aggregation)

5)maintain aesthetic quality

Why we need generalization in mapping?


6/28

Real world

Maps


7/28

What is the purpose of generalization?

1. the reduction in scope, amount, type andcartographic portrayal of mapped or encoded data

2. maintenance of graphical clarity at the target scale

3. basic principle of map generalization is toemphasis salient object AND omit less important

ones

4. ensure readability AND preserve geographical

meaning of the map as faithfully as possible.


8/28

How we perform generalization?

There is four main generalization operators , we usedthe four operators to achieve maximum and adequate

level of generalization.

The four operators (elements) were :-

i. Selection

ii. Simplification

iii. Exaggeration

iv. Classification


9/28

SELECTION Intellectual process of deciding whichclasses of features will be necessaryto serve the map purpose.

1. To limit our concern to those classes of features .

2.Wh

ich

elements remain depends on th

e purpose ofthe map.

3. No modifications take place


10/28


11/28

SIMPLIFICATION

y Determine important characteristics of featuresattributes and eliminates unwanted details.

y Two main objectives:-

1. We must reduce the amount of informationto the maps ability to portray it legibly at

the chosen scale. That is we must decide

how much information to portray.

2. We must maintain as far as possible the

essential geographical characteristic of the

mapped phenomena


12/28


13/28

CLASSIFICATION

Classification is ordering, scaling and grouping of featuresby their attributes and attributes values

The goal of classification is to exoress the

salient character of distribution.

Grouped the classes for comprehension and

ease of representation.


14/28


15/28

Green

Area

Academic

Area

Residential

Area

Commercial

Area

Technology

Park


16/28

EXAGGERATION

Enhancement of exaggeration of feature due toimportance and legibility requirements.

y The main objectives:-

1. We deliberately enlarge or alter a feature inorder to capture its real world essence.

2. It doesnt mean it should be as accurate as

the real one, but the portrayal should

possess real meaning or shape.


17/28

Map of Peninsula Malaysia


18/28

Map of Malaysia


19/28

Map of Southeast Asia


20/28

Map of Asia


21/28

World Map


22/28

What factors that effect generalization?

There is main four forces or factors which control

the process of generalization :-

1) Map Purpose & Conditions in Use2) Map Scale

3) Quality and Quantity of Data

4) Graphic Limits


23/28

1) Map Purpose & Conditions in Use

Before we construct a map, several basic questionshould be addressed;

Whatis the map for?

Is the map is studied or would be used for a long

period?Is the map designed to provide a great deal of

geographicinformation?

Is the map to portray particular distribution?

Will the display will be manipulated by the user?


24/28

2) Map Scale

There is a practical level of detail associated with anyscale.

Data captured at one scale are not transferrable to widely

different scales.

Data captured at a larger scale are too detailed forsmaller scales, and data captured at a small scale are too

generalised for larger scales.

DIRECT RELATION TO SCALE: the smaller scale,more generalization needed to be done to the

features selected.


25/28

1 : 50 000

1 : 12 500


26/28


27/28

3) Quality & Quantity of Data

Data quality and quantity also greatly affect thegeneralization in various ways:-

1. Quality of data affect the quality of the map produced

2. Accuracy of data sources also need to be consider

3. Lack or abundance of data (quantity matters) also canaffect maps performance

4. Cartographer should also determined the accuracy of the

data used for the maps construction


28/28

4) Graphic Limits

Another factors which affect the generalization process isgraphic limits. We can break these factors into two

groups:-

a) Technical limits by the cartographers tools

b) Perceptual limits of th

eh

uman eye

Our ability to form symbols from those elements is subject to three

types of limitations : a) pyhsical, b) physiological, and c)

psychological limits.

In digital cartography, graphic limits refer to the capacity of themonitor and software to perform the generalization

lecture 08 generalization

Documents