Map Design GIS

Cartography

• The art and technique of making maps

  • The who, what, where, and how we may present information

What does Cartography depend on

• Intended Audience

• Information to communicate

• Area of interest

• Physical and resource limitations

Cartography must consider

• Data to plot

• Symbols shapes, sizes, or patterns

• Labeling and font type and size

• Legend properties, size, and borders

• The placement of all these elements on a map

Slocum’s Map Elements: key map features

Scale, size, shape, and other general map properties

Map scale

• relationship between distance on the map and actual distance on the ground

  • allows for navigation, calculating area, and comparing sizes

  • distortions mean scale can never be exactly correct on the entire map

Three map scale types

• graphic map scale

• fractional map scale

• verbal map scale

large scale map

• relatively large representative fraction

  • used to show a small portion of Earth’s surface

  • used to show detail

Small-scale map

• small representative fraction

  • used to show a relatively large area

  • imits detail

Dot map

one of the first examples of GIS and the birth of modern Epidemiology

Isopleth Map

any line on a map connecting points with equal values of a particular variable (temperature, dew point, etc.).

Isobar

A line that connects points of equal pressure

Isotherm

A line that connects points of equal temperature

Isotach

A line that connects points of equal wind speed

Isohyet

A line that represents rainfall

Gestalt of map design

Map consists of elements

Human cognition is based on clumping

Elements seen both individually and holistically

Eye seeks similarity, proximity, continuity, closure 

Symmetry, simplicity, balance favored

Examples of using maps to lie

propaganda, commercial lies, gerrymandering

Hue

the “color” of the color

Saturation

intensity of the color

desaturated colors tend to look

gray

value

the lightness or darkness of a color

Design principles

• don’t rely only on color to convey information

• Keep it simple

• Avoid using these colors in close proximity

• Red & green

• Blue & purple

• Blue & gray

• Green & brown

• Green & blue

• Green & black

Qualitative color scheme

• Good for nominal not appropriate for ordered or numerical

• The distinction between classes becomes visible through variations in hue

• Ideally with no or slight lightness differences between colors. If a class needs to be highlighted it is possible to use a darker or more saturated color to visualize it

sequential color scheme

• applied to ordered, often numerical data

• Lighter colors for lower values or rank

Diverging color scheme

• often described as a combination of two sequential schemes with a critical break point in the middle.

• The two sequences “diverge” from a shared light color that stresses important mid-ranges in the data. The two extremes are visualized by contrasting dark hues while changes in lightness are used to display intermediate values.

• Common examples of data suitable for diverging color scales are temperature variations and stock exchange dynamics

NATURAL BREAKS

• a kind of “optimal” classification scheme that finds class breaks that (for a given number of classes) will minimize within-class variance and maximize between-class differences.

• One drawback of this approach is each dataset generates a unique classification solution, and if you need to make comparison across maps, such as in an atlas or a series (e.g., one map each for 1980, 1990, 2000)

• you might want to use a single scheme that can be applied across all of the maps.

Manual data breaks

• There are many times we need to manually set one or all of the class breaks.

• Are there important breakpoints that need to be “hardwired” into your class breaks?

• Does one of the class breaks need to be the mean?

• Is this map part of a series that needs the same classes across all of the maps (so that the colors always refer to the same numbers on any map)?

• Do any of the other methods get you close to a good solution that could be improved with a few slight adjustments in those classes?

• If so, do not hesitate to set these class breaks yourself