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GIS OUTPUTCartographic Principles:

Map Design and Production

GEOG 350 / 550: Geographic Information Science

With acknowledgement of M. Dodge, CASA, UCL

It’s a Map, Map, Map World• More maps are available than at any time in

history• The Map is not the territory• Finding the right map can be hard• Distribution of map coverage is uneven

– Especially in developing world

• Sources of hardcopy maps– Map libraries, National Geographic Society, West

Virginia Geological and Economic Survey (Mont Chateau)

– Map shops– Raven Maps www.ravenmaps.com/ – Oddens map list, http://oddens.geog.uu.nl/

The Problem of Accuracy.• In "On Exactitude in Science", Jorge Luis Borges

describes the tragic uselessness of the perfectly accurate, one-to-one map:• “In time, those Unconscionable Maps no longer

satisfied, and the Cartographers Guild drew a Map of the Empire whose size was that of the Empire, coinciding point for point with it. The following Generations, who were not so fond of the Study of Cartography saw the vast Map to be Useless and permitted it to decay and fray under the Sun and winters. In the Deserts of the West, still today, there are Tattered Ruins of the Map, inhabited by Animals and Beggars; and in all the Land there is no other Relic of the Disciplines of Geography”

• Lewis Carroll on maps

A Map Anyone Can UnderstandHe had bought a large map representing the sea,Without the least vestige of land:And the crew were much pleased when they found it to beA map they could all understand

"What's the good of Mercator's North Poles and Equators,Tropics, Zones and Meridian Lines?"So the Bellman would cry: and the crew would reply,"They are merely conventional signs!"

"Other maps are such shapes, with their islands and capes!But we've got our brave Captain to thank`"(So the crew would protest) "that he's bought us the best -A perfect and absolute blank!"

From: Fit the Second, The Bellman's Speech in The Hunting of the Snark by Lewis Carroll

www.lib.utexas.edu/maps.index.html Topographic Map

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Navigational Chart, Bathymetry Thematic Map – Simple Cartographic Analysis

Hybrid

Thematic Map and Image

Graphicacy• Literacy, numeracy and oral skills• World of screens, monitors and interfaces

graphicacy is becoming more important • Understanding maps

– need graphicacy

• Graphicacy skills of map-makers and map-users• Said to be inherent skill,

– but some are better than others. artistic flair, designer eye for form and layout

• Everyone is potentially a map-maker. – Can’t rely on the skills of professional cartographers

How maps work• Abstractions to make a ‘scale model of reality’

– c.f. famous fictional stories of the 1:1 maps selection

• 1. Classification (grouping similar features) to reduce complexity and organize information

• 2. Simplification• 3. Symbolization• these are design processes (and are inherently

subjective)• there is no one true map of a phenomena or place

Design• There are some (scientific) rules in map design,

but much artistic judgment in terms of – selection of colors– symbology– labeling (format and position) – arrangement of overall layout– (plus data selection, projection, scale, etc)

• Subtle changes in design (e.g. weight of a label font for particular objects) can yield big changes in how the map is read

• Use (and mis-use) the power of design. Ethical practices not to deliberately deceive

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Design and ‘dangers of defaults’• Modern GIS, mapping, drawing software is

very flexible and powerful• but still constrains design• always question software defaults settings

Tufte’s principles of graphical excellence

• show the data• induce the reader to think about the substance

rather than the methodology, graphic design, gee-whiz technology

• avoid distorting what the data have to say• present many numbers in a small space• make large datasets coherent• encourage the eye to compare different pieces

of data

Tufte’s principles of graphical excellence

• reveal the data at several levels of detail, from broad overview to the fine structure

• serve a reasonably clear purpose: description, exploration, tabulation or decoration

• be closely integrated with the statistical and verbal descriptions of a dataset

Mapping Basics• assumption of maps made for presentation

– need to be usable for general audience

• map layout• map scale and generalization• symbolization and graphic variables• choropleth mapping & data classification• color• labeling and typography

GIS Processing Transformations Characteristics of Map

• Two main types– Topographic– Thematic

• Some map problems– Can miscommunicate– Each map is just one of all possible maps– Complex maps can be difficult to understand

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Topographic – Base map Thematic map - Choropleth

Map layout• For presentation maps, some conventions on

what to include:– a title (or caption). clearly state what the map

shows. plus relevant date of data, sources, missing values, author, contact info, etc

– a legend, so any reader can interpret the content of the map. meaning of all symbol and colors

– scale indication. translates distance on the map to distance on the ground

– orientation indication (the good old north arrow)– borders and neatlines

• these conventions are widely broken! TitleLegend

Projection

Grid

Data Source

Inset map

Map Body

Author

North Arrow

Scale

Balance and centre

• Visual impact of arrangement. harmonious arrangement around the optical centre

• concern for weight and direction of objects around the ‘natural’ centre

• unbalanced composition look random and accidental

optical centre

geometric centre

Golden proportions

11.618

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Interesting balance Map scale• what level of detail is shown• crucial to choose appropriate scale to work at• large scale map : small surface area in high

detail (e.g. city plans)• small scale : large surface area in low detail

(e.g. national road atlas)• scale represented as a statement (“one inch

equals five miles”), a graphical scale bar, (useful for measuring lengths), or as a representative fraction (1:1250)

• very few maps use scale consistently for every object

Key Modes of Generalisation

• Distortion is inherent,inevitable, unavoidable

•May have to leavefeatures off the mapAltogether - selection

• Avoid visual clutter,balance content andlegibility

Map Symbolization

• Graphic language (of points, lines, polygon, icons and text) used to represent ‘real’ features on the map

• Legibility (‘practical’)• Harmonious (‘pretty’)• Symbols can be iconic, geometric or abstract• Symbol selection is creative aspect of design, wide

choice and few firm rules• Symbols can have several different dimensions

(properties or characteristics) which encode meaning• Symbols can have quantitative or qualitative meaning

Bertin's Graphic Primitives

Graphic Variables for Symbols• Shape, size, orientation• Color hue, color value, color saturation, pattern• and location

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(Source: Larry Landweber, http://www.cs.wisc.edu/~lhl/maps/)

Choropleth Maps• Spatial counterpart of histogram• Aggregate data, usually ratio or percentage

– NOT raw counts

• Data map for discrete spatial units• choro from choros (place) and pleth (value)• Practical Issues

• choice of intervals - number and their breaks• equal interval, equal share (quantiles), standard deviational,

…

• Choice of colors• important for perception of patterns

• Misleading role of area of spatial units• larger areas “seem” more important

Choropleth Maps• Very widely used. the ‘default’ mapping, especially

for social data (e.g. census)• Most mapping tools produce choropleth maps• Easy produced in GIS, stats software• Not necessarily the best solution• Problems:

• can easily promote false notions of homogeneity inside the zones and sharp cut-off at the borders. real phenomena (e.g. Internet access) do not fit neat set of units

• Should be used for ratio data and not absolute counts as most spatial units are variable in size

Data Classification• Classification is a key method of abstracting

reality into simplified map• method of classification is important as effects

‘look’ of the map• classification scheme can easily be

experimented with (manipulated?) to give the pattern you want

• classification should ‘match’ data distribution• number of classes. can reader interpret

between them? recommended max of 6• distribution of zones into classes

Choropleth Class Schemes

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Classification Options from ArcMap

• natural breaks (Jenks method),

• quantiles, • equal interval, • standard deviation

• See handout from Dent (1999, page 145)

The Role of CCoolloorr• Color is one of most exciting aspects of design• Color perception is a combination of

physiological (sensing in the eye and cognitive processing) and psychological reactions

• Color evoke emotions. subjective reaction to color

• Connotative meanings of color. See Dent (1999, page 295)

Defining Color

• Cultural specific• also color blindness, • 7% men and 1% women

• Warm colors (red, orange, yellows)• Cool colors (violet, blue, greens• defining color:- hue, saturation, value (HSV) model

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hue - basic color weperceive, eg 12 stepwheel

value - lightness ordarkness. Can be hardto perceive variationsin value

saturation - intensity orpurity compared to aneutral gray

Design and color• Gives structure and readability• Developing figure and ground relationships

– warm color better for figures. Said to ‘advance’ to viewer. Cool colors tend to recede

• Perceptual grouping of like features through color

• color contrasts. using value or saturation to represent data on thematic maps

• qualitative conventions - blue for water, green for lush vegetation; red = warm and blue = cool in temperatures; hill shading

Labeling the Map• lettering choice can have a significant impact to

effectiveness of the map • typography - practical and ‘personality’• map text to label features has several key

parameters– font typeface, size spacing– placement and orientation

• importance of type discernibility • map labels can communicate important data, e.g.

hierarchy of features, implying importance • Chislehurst, Bromley, L O N D O N• manual labeling of features can get very tedious.

but automatic label placement is still far from perfect

Think about different types of lettering styles and placement/orientations used and the effects it has

Some Considerations• from Dent (1999, page 271)

– legibility of individual letters is of paramount importance, especially in smaller type sizes. Choose a typeface in where there is little chance of confusion between c and e and i and j

– select a typeface with a relatively large base height– avoid extremely bold forms– choose a typeface that has softer shading; extreme

vertical shading is more difficult to read than rounder forms

– do not use decorative typefaces on the map as they are difficult to read

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Map Production System Information Flows

Code of Ethics1. Always have a straightforward agenda, and have a defining purpose or goal

for each map2. Always strive to know your audience, the potential/likely map users3. Do not intentionally lie with data4. Always show relevant data whenever possible 5. Data should not be discarded simply because they are contrary to the

position held by the cartographer6. At a given scale, strive for an accurate portrayal of the data7. The cartographer should avoid plagiarizing; report all data sources 8. Symbolization should not be selected to bias the interpretation of the map9. The mapped result should be able to be repeated by other cartographers10. Attention should be given to differing cultural values and principles

Dent (1999, page 19)

Maps for Peace – or war

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Conclusions

• Cartography is both an art and a science• Maps are fundamental to GIS projects

– They remain the predominant output• Cartographic software makes it easy to

produce good and bad maps• New technologies and the Internet continues

to change the content and techniques of GIS-based cartography

Further reading– Paul Longley et al. (2005) Geographic Information

Systems and Science, 2nd edition, Chapter 12– Borden Dent, (1995) Cartography: Thematic Map

Design, fifth edition– Terry Slocum, (1999) Thematic Cartography and

Visualization– Menno-Jan Kraak and Ferjan Ormeling, (1996)

Cartography: Visualization of Spatial Data