Colour in map design by Alastair Pearson

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Colour in map designbyAlastair Pearson
Geographical Data Presentation
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Reasons for concern

• Colour graphics more affordable
• Unlimited freedom to select, mix and use colour
• Poor guidelines with software
• Unhelpful colour descriptions - wheels, triads,
  RGB settings)
• Poor default colours

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Functions of colour in map design

• Robinson (1967)
• 1. Simplifying and clarifying agent.
• Development of figure-ground organization
• 2. Affects the perceptibility of the map.
• Legibility, visual acuity, and clarity.
• 3. Elicits subjective reactions to the map.
• People respond to colours - connotative and
  subjective.

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Functions of colour in advertising

• Attract buyer's attention
• Stimulate interest
• Identify products
• Relate successive advertising
• Provide emphasis
• Illustrate, interpret and prove
• Lead reader's attention
• Embody prestige
• Functions of design for mapping are similar.

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What is colour?

• a complex eye-brain response to
  electromagnetic radiation in the visible portion
  of the electromagnetic spectrum, commonly called
  'light'

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• human perceives light 400nm to 700nm (1nm
  1/1000 of a micron) in wavelength
• 6 "spectral" colours - violet through red
• colour of objects functions of-
• illumination source
• object's reflectance ability
• sensitivity of cones in our eyes

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Spectral Colour circle

• usually visible colours only
• mix opposite colours GREY (complementary)

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Additive colour mixture

• mixing light
• additive colour primaries (RED, GREEN, BLUE)
• mix primaries to produce almost any colour
• vary energy level

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Subtractive colour mixture

• mixing pigments
• absorb and reflect parts of spectrum
• subtractive colour primaries (CYAN, MAGENTA,
  YELLOW)
• mix primaries to produce most colours
• vary quantity

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Colour specification systems

• Early systems - subjective/psychological
• Later systems - objective/physical spectrometry
• Increasing use
• cartographers need to specify exact colour
  specifications
• researchers in cartography need to refer to the
  same colour
• systems enable us to conceptualise
  interrelationships of hue, brightness and
  saturation

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2 worthy of note -

• (i) C.I.E. Colour Specification
• (ii) Munsell Colour Solid - N.America

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(i) C.I.E. COLOUR SPECIFICATION (Commission
International de l'Eclairage)

• physical colour specification system
• describes physical properties of colour
• specified in numerical terms
• measures mix 3 additive primaries in varying
  intensities (tristimulus values)

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Summary-

• objective system
• specifies each colour precisely
• based on additive light
• not based on human visual perception
• not that relevant to cartographers

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(ii) Munsell Colour Solid (Albert H. Munsell
1858-1918)

• 3D representation of colours
• hue, value, saturation are axes
• based on human visual perception
• equal visual steps

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Description

• Hue
• 100 hues in circle
• 10 major hues (5 principle, 5 intermediate)
• ordered according to spectrum
• Value
• vertical axis
• 0-10
• 0 BLACK
• 10 WHITE

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• Chroma
• horizontal axis
• 0-14 or 16
• 0 grey
• 14 or 16 pure hue (full saturation)
• EXAMPLE 5.0 YR 6 10

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Summary-

• a) subjectively/psychologically based
• b) human colour perception
• c) equal steps in appearance not physical reality
• d) referred to by cartographers - thematic
  mapping - equal visual steps

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Printing colour specifications

• colour specification systems difficult to use in
  production
• cartographer uses colour matching systems
• cartographer specifies inks

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Pantone Matching System

• 8 basic colours black and white
• over 500 colours
• each colour coded
• over 500 printing ink hues are possible

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3 and 4 colour process

• feasible to print map using as many inks as
  colours
• cartographers use screens and overprinting to
  create value, chroma and often hue variation
• printing often uses 3 or 4 colour process
• CYAN, MAGENTA, YELLOW BLACK
• BLACK often added - 4 colour process
• screens regulate process colour
• colour charts provide guide

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Colour on video displays

• Combines additive primaries (red,green,blue)
• RGB Colour System- RED,GREEN,BLUE
• gun for each colour fires electron beam
• phosphor dot for each colour
• 3 dots - 8 colours possible
• vary with 256 intensities 16.7 million colours
• 256 colours normal limit

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Qualitative conventions

• Robinson (1967) colour conventions and
  associations
• Blue for water
• Red with warm, blue with cool
• Yellow and tans for dry and little vegetation
• Brown for land surfaces and contours
• Green for lush and thick vegetation

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Quantitative conventions

• Cuff (1972) identifies four colour plans
• 1. Grey and simple hue vary colour brightness
  only.
• 2. Part-spectral plan colours adjacent on colour
  wheel show variations in amount
  (blue-green-yellow / red-orange-yellow)
• 3. Full-spectral plan separate hue used to
  represent amounts (red, orange, yellow, green and
  blue for hypsometric tints)
• 4. Double ended plan to illustrate bi-variate
  data or positive and negative data values (Dark
  red to light red then light blue to dark blue)

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Possible solutions to misuse of colour (Green,
1993)

• More input of cartographic expertise
• More education and training in cartography to
  raise awareness and knowledge
• More online tutorial and expert advice available
• More software packages with emphasis on
  cartographic tools and applications
• More research into map design in an electronic
  medium