The cartographic method

• • Context The cartographic method • Understanding • Data analysis and design • at work Menno-Jan Kraak • Beware!

Faculty of Geoinformation Science and Earth Observation

Cartography Why maps?

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visualization process cartographic method How do I say What to Whom, and is it effective? November 26

Geographic Data

dorp Cartography is the art,art, science and and technology technology of ofmaking making and and using using maps maps Why maps? Why maps?

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

• The spatial layout of maps enable users to see:

• patterns

• relationships

• trends 1985

1965

weather: wind speed personal landscape preferences http://www.knmi.nl/actueel/ http://www.daarmoetikzijn.nl/

Maps, constraints and variables

goal / purpose user data use environment of map charactersitics characterisitcs Context

contents scale projection accuracy interface

map design Context: maps to present Presentation

• start: facts to be presented • For presentation, communication of the map contents can be are fixed optimized by applying cartographic design rules for the translation of • process: choice of data into graphics appropriate visualization • Guided by: ‘How do I say what to whom, and is it effective?’ technique

• result: high quality What Information Effective visualization presenting Cartographic Info retrieved facts, the single best map Information Analysis • emphasize: on map design Evaluation I Cartographer User How Cartographic Whom Sign System Map Say

Context: maps to explore Exploration

• start: data without • Map as interface to the data hypothesis about the data • Map in context • process: interactive, undirected search for structures and trends • result: visualization that provides hypothesis, different alternative views • emphasize: enabling ‘discoveries’ Exploration

What Information Effective Cartographic Info retrieved Information Analysis Understanding Evaluation I CartographerI CartographerUser Whom User How Cartographic Whom Sign System Map Say

Understanding maps Understanding which map to use

40 minutes by 3 minutes underground walking Understanding what has Understanding what to map? been mapped?

• day

• night

Understand need for design Understanding your limitations Understanding your possibilities Understanding your data

[source: New York Times]

Method: data analysis and design

determine link select

geographical measurement perceptual visual Data analysis data scales properties variables and design

choice of representation method ( type of map ) MEASUREMENT Importance of correct design ratio Data and LEVEL > Which province has most inhabitants? interval implicit

ordinal Number of inhabitants distinguishing Numbera) of inhabitants Population of Estonia’s provinces in 2012 nominal << 10,000 10,000

10,00010,000 -<80,000 -<80,000

80,000-<80,000-< 500,000 500,000 -15ºC PERCEPTUAL

<< 500,000 500,000 -5ºC order PROPERTIES distance proportion differentiation

a) nominal c) interval 2 dimensions / plane hamlet and road temperature size h i g h

value > grain / texture l o w Number of inhabitants colourcolor > 500,000 0 50 km b) ordinal d) ratio 0 50 km b)c) high and low number of students orientation

shape / form 80,000-< 500,000 0 50 km

10,000 -<80,000 Population of positive VISUAL < 10,000 Estonia’s provinces in 2012 perception VARIABLES

Data analysis and map symbols Example data

data Harjumaa Lääne- Ida-Virumaa Virumaa

Järvamaa invariant components Hiiumaa Läänemaa Raplamaa PERCEPTUAL VISUAL BASIC Jõgevamaa map title MEASUREMENT LEVEL PROPERTIES VARIABLES SYMBOLS LENGTH RANGE Pärnumaa nominal size Saaremaa Viljandimaa Tartumaa point legend (qualitative) differentiation value order texture line ordered distance color area M A P interval Põlvamaa proportion orientation text Valgamaa ratio shape (quantitative) Võrumaa geo

a) b) Design: visual hierarchy

Population of the province of Tartu Population of the province of Saaremaa in comparison with other Estonian provinces in comparison with other Estonian provinces

Ida- Harjumaa Harjumaa Lääne- data invariant Virumaa Population by Province Virumaa Lääne- Virumaa Ida- Virumaa Läänemaa Järvamaa Hiiumaa Hiiumaa Raplamaa Järvamaa Raplamaa components Jõgevamaa Läänemaa PERCEPTUAL VISUAL BASIC Jõgevamaa MEASUREMENT LEVEL Pärnumaa PROPERTIES VARIABLES SYMBOLS

Saaremaa Pärnumaa Viljandimaa Tartumaa Viljandimaa Tartumaa LENGTH RANGE Saaremaa nominal size (qualitative) differentiation point Põlvamaa value Põlvamaa order Valgamaa ordered texture line distance color area Valgamaa interval 550000 Võrumaa 550000 AMOUNT proportion orientation text Võrumaa ratio 8482-552972 shape

(quantitative) number on inhabitants number on inhabitants

geo 15 150000 150000

50000 50000 10000 0 50 km 10000 0 50 km

symbol Tartu all information map title / legend other provincial symbols provincial names a) b) base map

Correct design? Important map types

inhabitants per km2 Estonia’s population density in 2012 8 - 12 • Choropleth 13 - 24 25 - 73

74 - 128

0 50 km a) • Qualitative map

a) b)

• Proportional point symbol map (diagram map)

c) d) types Convert

Common mistakes

inhabitants per km2 Estonia’s population density in 2012 number of inhabitants Estonia’s population in 2012 8 - 12 < 10,000

13 - 24 10,000 -<80,000

25 - 73 80,000-< 500,000

74 - 128 > 500,000

Maps at work

0 50 km b) 0 50 km c) Backgrounds On-line tools

Scale - zoom levels Compare location

2 4 6 8

10 12 14 16 Compare attribute Compare time

Compare and understand

Beware!

http://www.zorgatlas.nl Qualitative maps - caution Choices to be made: absolute or relative quantities

• 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

Scale & placename patterns Geographical units

http://bl.ocks.org/pramsey/922f6170dec2a3cd5da6 Interpreting maps Borders

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

unemployment unemployment More than 8% More than 8% Less than 8% Less than 8%