Symbols and The Visual Variables

Question 1

3 dimensions

Answer 1

0-dimensional = points
1-dimensional = lines
2-dimensional = areas

Question 2

Graphic variables

Answer 2

• form = variation on external shape, orientation and internal structure
• dimension = variation in size
• colour = hue (wavelength), lightness, saturation
• pattern = visual repetition of pattern elements
• texture = course to fine

Question 3

Colour

Answer 3

Formed by either:

• light generated by something
• light reflected from a surface

Wavelength determines what colour we see

Question 4

Colour attributes

Answer 4

• hue: depends on wavelength
• lightness (value):total amount of light reflected
• saturation (chroma): purity of light reflected. Varies from grey to pure colour

Question 5

Subtractive primaries

Answer 5

Most commonly thought of - paints and inks - cyan, magenta and yellow. When light hits the surface some of it is absorbed others reflected = subtracting some of the wavelength. Black essentially reflects no light. Too many colours = more wave length absorbed

These colours are easier to see because they we used when young

Question 6

Additive colours

Answer 6

Light generated - adding wavelengths. This will ultimately result in white. E.g light computer displays. Red, green and blue. Difficult colour space to use in a practical sense

Question 7

Colour in printing

Answer 7

Mix ink until colours were achieved. This was expensive as this needed a printing plate for each colour - used up until the 1960s.

Subtracting primaries are now used as it can print different densities of ink of areas to create tints. Produced by fine dots or line patterns. Gives variation in light

Printing on white paper ink an produce more colours with different tints.

Question 8

Process colour

Answer 8

Based on subtractive primary colours CMY. Combination of all inks give dark brown. Therefore there is a black ink (K) for a true black. This is known as a process colour or CYMK.

The dominant process since 1990s. Most printing uses process colours. On screen colours are formed differently

Question 9

Graphic semiology

Answer 9

Study of graphic sign systems. There isn’t one unifying theory. Different authors describe different sets of graphic variables.

Question 10

Bertin

Answer 10

One of the first person to describe graphic variables. He described 7:

• form/shape
• orientation
• couleur - colour hue
• grain like texture
• valueur - colour lightness
• Taille - size
• position

Position has be been argued to not be a cartographic variable as you cannot alter a map to make it a better balance

Question 11

Bertin’s perception of image. 4 ways:

Answer 11

Associative = uniformity
Selective = separate the field
Ordered = natural hierarchy
Quantitative

Question 12

DiBase and MacEachren 1991 & 94

Answer 12

• colour value (lightness)
• colour saturation
• arrangement
• focus

Saturation was not widely used until now as it was used to represent value of data I.e. Choropleth maps

Question 13

Representing qualitative data

Answer 13

Change of form. Structure or pattern

Change of hue

Change of orientation

Question 14

Representing rank or ordering

Answer 14

Variation in dimension or lightness

Size doesn’t relate to value

Question 15

Representing quantitative data

Answer 15

Change in dimension

Change in lightness

Question 16

Relationship to symbol

Answer 16

• abstract/geometric - no relationship
• concept related - linked to idea of feature (cup)
• image related - picture of object (tree)

Question 17

Control of contrast

Answer 17

Similar things should appear similarly ins more different in attributes should be shown with greater difference

Question 18

What does the graphic represent

Answer 18

Make it easier for the reader (pictographic symbols and colour associations)

‘Conventional’ symbols - use familiar to them

Standard symbol - some subject have well established standards