Faculty of Geoinformation Science and Earth Observation

The cartographic method

Menno-Jan Kraak

The cartographic method

• Cartography

• Context

• Understanding

• Data analysis and design

• Maps at work

• Beware!

Cartography

Geographic Data

visualization process

How do I say What to Whom, and is it effective?

Map

November 26

French troops

Cartography is the art, science and technology of making and using mapsCartography is the art, science and technology of making and using maps

cartographic method

Why maps?

dorp

• Maps are abstractions or models of reality, in which geographic space is represented by map space

• The spatial layout of maps enable users to see:

• patterns

• relationships

• trends

Why maps?

1965

1985

• Make invisible things visible

Why maps?

personal landscape preferences http://www.daarmoetikzijn.nl/

weather: wind speed http://www.knmi.nl/actueel/

Context

Maps, constraints and variables

goal / purposeof map

data characterisitcsuse environmentuser

charactersitics

contents scale projection accuracy interface

map design

• start: facts to be presented are fixed

• process: choice of appropriate visualization technique

• result: high quality visualization presenting facts, the single best map

• emphasize: on map design

Context: maps to present

• For presentation, communication of the map contents can be optimized by applying cartographic design rules for the translation of data into graphics

• Guided by: ‘How do I say what to whom, and is it effective?’

Presentation

CartographicInformation

Analysis

CartographicSign

System

Evaluation

Effective

Whom

Say

How

I

WhatInformation

User

Map

Cartographer

Info retrieved

• start: data without hypothesis about the data

• process: interactive, undirected search for structures and trends

• result: visualization that provides hypothesis, different alternative views

• emphasize: enabling ‘discoveries’

Context: maps to explore

• Map as interface to the data

• Map in context

Exploration

Exploration

CartographicInformation

Analysis

CartographicSign

System

Evaluation

Effective

Whom

Say

How

I

WhatInformation

User

Map

Cartographer

Info retrievedCartographicInformation

Analysis

CartographicSign

System

Evaluation

Effective

Whom

Say

How

I

WhatInformation

User

Map

Cartographer

Info retrievedUnderstanding

Understanding maps Understanding which map to use

40 minutes by underground

3 minutes walking

• day

• night

Understanding what to map?

Understanding what has been mapped?

Understand need for design Understanding your limitations

Understanding your possibilities

[source: New York Times]

Understanding your data

Data analysis and design

Method: data analysis and design

geographicaldata

measurement scales

perceptualproperties

visualvariables

determine link select

choice of representation method

( type of map )

Data and perception

PERCEPTUALPROPERTIES

ratio

interval

ordinal

nominal

differentiation

order

distance

proportion

implicit

distinguishing

MEA

SUR

EMEN

T LEV

EL

>

2 dimensions / plane

size

value

grain / texture

colour

orientation

shape / form

2 dimensions / plane

size

value

grain / texture

color

orientation

shape / form

positive perception

VISUALVARIABLES

a) nominalhamlet and road

b) ordinalhigh and low

>

l o w

h i g h

c) intervaltemperature

d) rationumber of students

-5ºC-15ºC

Importance of correct design Which province has most inhabitants?

< 10,000

10,000 -<80,000

80,000-< 500,000

> 500,000

0 50 km

Population of Estonia’s provinces in 2012

Number of inhabitants

a)< 10,000

10,000 -<80,000

80,000-< 500,000

< 500,000

Population of Estonia’s provinces in 2012Number of inhabitants

0 50 km b)

< 10,000

10,000 -<80,000

80,000-< 500,000

< 500,000

0 50 km

Population of Estonia’s provinces in 2012Number of inhabitants

c)

Data analysis and map symbols

data

componentsinvariant

intervalratio

(quantitative)

ordered

nominal(qualitative)

RANGELENGTH

map title

legend differentiationorder

distanceproportion

pointlineareatext

sizevalue

texturecolor

orientationshape

geo

M A P

MEASUREMENT LEVEL PERCEPTUAL PROPERTIES

BASICSYMBOLS

VISUALVARIABLES

Example data

Harjumaa

Hiiumaa

Ida-Virumaa

Järvamaa

JõgevamaaLäänemaa

Lääne-Virumaa

Pärnumaa

Põlvamaa

Raplamaa

Saaremaa Tartumaa

Valgamaa

Viljandimaa

Võrumaa

a) b)

data invariant

intervalratio

(quantitative)

ordered

nominal(qualitative)

RANGELENGTH

Population by Province

differentiationorder

distanceproportion

pointlineareatext

sizevalue

texturecolor

orientationshape

geo

PERCEPTUAL PROPERTIES

BASICSYMBOLS

VISUALVARIABLES

8482-552972

components

15

AMOUNT

MEASUREMENT LEVEL

Design: visual hierarchyPopulation of the province of Tartu

in comparison with other Estonian provinces

550000

150000

5000010000

number on inhabitants

550000

150000

5000010000

number on inhabitants

0 50 km 0 50 km

Harjumaa

Hiiumaa

Ida-Virumaa

Järvamaa

Jõgevamaa

Läänemaa

Lääne-Virumaa

Pärnumaa

Põlvamaa

Raplamaa

Saaremaa Tartumaa

Valgamaa

Viljandimaa

Võrumaa

Harjumaa

Hiiumaa

Ida-Virumaa

Järvamaa

JõgevamaaLäänemaa

Lääne-Virumaa

Pärnumaa

Põlvamaa

Raplamaa

Saaremaa Tartumaa

Valgamaa

Viljandimaa

Võrumaa

Population of the province of Saaremaain comparison with other Estonian provinces

all information symbol Tartumap title / legendother provincial symbolsprovincial namesbase mapa) b)

Correct design?

a) b)

c) d)

• Choropleth

• Qualitative map

• Proportional point symbol map

(diagram map)

Important map types8 - 12

13 - 24

25 - 73

74 - 128

inhabitants per km2

0 50 km

Estonia’s population density in 2012

a)

Thematic map types Convert

Common mistakes

8 - 12

13 - 24

25 - 73

74 - 128

inhabitants per km2

0 50 km

Estonia’s population density in 2012

b)

number of inhabitants

0 50 km

Estonia’s population in 2012< 10,000

10,000 -<80,000

80,000-< 500,000

> 500,000

c)

Maps at work

Backgrounds On-line tools

Scale - zoom levels

2 4 6 8

10 12 14 16

Compare location

Compare attribute Compare time

Compare and understand

http://www.zorgatlas.nl

Beware!

• Impression of non-area related phenomena may be wrong because it is influenced by the size of the areas (e.g. dominant language spoken: related to people, not to area)

• Use a cartogram

Qualitative maps - caution Choices to be made: absolute or relative quantities

Scale & placename patterns

http://bl.ocks.org/pramsey/922f6170dec2a3cd5da6

Geographical units

Interpreting maps Borders

Order Errors

‘Errors’ due to (misuse of) mapping method: design error?

More than 8% Less than 8%

unemploymentMore than 8% Less than 8%

unemployment