Map Design and Symbology in GIS Environment

Asib Ahmed ([email protected])

Lecture 1, Wednessday 16th April 2014

There are some (scientific) rules in map design but much artistic

judgement in terms of

◦ selection of colours

◦ symbology

◦ labelling (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

1. Classification

2. simplification

3. symbolization

1. Map layout

2. Map scale and generalisation

3. Symbolisation and graphic variables

4. Choropleth mapping & data classification

5. Colour

6. Labelling and typography

For presentation of 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 colours

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

◦ orientation indication (the good old north arrow)

◦ borders and neatlines

1

1.618

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 leave

features off the map

altogether

• avoid visual clutter,

balance content and

legibility

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

shape, size, orientation

colour hue, colour value, colour saturation, pattern

and location of course

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

choro from choros (place) and pleth (value)

counterpart of histogram

aggregate data, usually ratio or percentage

data map for discrete spatial units

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

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

Same data plus

different classification

equal different looking

choropleth map!

• natural breaks

(Jenks method)

• quantiles

• equal interval

• standard deviation

colour is one of most exciting aspects of design

colour perception is a combination of physiological

(sensing in the eye and cognitive processing) and

psychological reactions

colour evoke emotions. subjective reaction to colour

connotative meanings of colour. See Dent (1999, page

295)

cultural specific. also colour blindness. 7% of men and

1% of women

warm colours (red, orange, yellows)

cool colours (violet, blue, greens

defining - hue, saturation, value (HSV) model

hue - basic colour we

perceive, eg 12 step

Wheel

saturation - intensity or

purity compared to a

neutral gray

value - lightness or

darkness. Can be hard

to perceive variations

in value

gives structure and readability

developing figure and ground relationships

◦ warm colour better for figures. Said to ‘advance’ to viewer.

Cool colours tend to recede

perceptual grouping of like features through colour

colour 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

lettering choice can have a significant impact to effectiveness of the map

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 labelling 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

◦ 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

1. always have a straightforward agenda, and have a defining purpose or

goal for each map

2. always strive to know your audience, the potential/likely map users

3. do not intentionally lie with data

4. always show relevant data whenever possible

5. data should not be discarded simply because they are contrary to the

position held by the cartographer

6. at a given scale, strive for an accurate portrayal of the data

7. the cartographer should avoid plagiarizing; report all data sources

8. symbolization should not be selected to bias the interpretation of

the map

9. the mapped result should be able to be repeated by other

cartographers

10. attention should be given to differing cultural values and

principles

◦ 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