Visualizing Data

Displaying patterns in complex datasets, communicating aspects we think are important.

Cartography

The art and science of making maps.

  • Why do we make maps?
    • To transmit spatial information to a map reader
  • Data and analyses are meaningless, unless conveyed effectively
    • Decide what you want to communicate and to whom

Cartography

Good Maps

  1. Concise
  2. Accessible
  3. Aesthetically pleasing

Bad Maps

  1. Cluttered, ineffective, misleading
  2. Inaccessible to target audience
  3. Ugly

A Bad Map

Excellent example of a bad map showing really interesting information.

  • Too much information
  • Too many colors
  • Text is way too small

A Better Map

Cleaner, less complex presentation.

  • Too much information
  • Too many colors
  • Text is way too small

TopHat Question 1

Cartography is the ___ and ___ of making maps.

Design Principals

Give the viewer the most information in the shortest time with the least ink in the smallest space.

  • Complex ideas communicated with clarity, precision, and efficiency.
  • Maximize data-to-ink ratio (i.e. more data, less other stuff).
  • Erase non-data ink, within reason.

Design Principals

The best maps can be interpreted quickly and easily.

  • Title: Clear and to the point
  • Content: Patterns are obvious, no "extra" information

Design Principals

The best maps can be interpreted quickly and easily.

  • Content: Takes longer to read, but subject matter is more complex
    • Minimizes "extra" information
    • Simplifies geometry

Data Symbolization

The techniques we use to represent information on a map.

  • The choices we make will convey aspects of the data
    • Color & brightness
    • Shapes & lines
    • Characters & fonts
    • Position & size
  • Some choices may lead to assumptions being made about the data
    • Intentionally or otherwise

Color

The HSV scale describes three components.

  • Hue: the dominant wavelength
    • Typical association with the term "color"
  • Saturation: the intensity of one color
    • All red or only a little red?
  • Value: the brightness of one color
    • Lightness or darkness, how much light is reflected?

Color Choice

It is important to choose the right kind of color map.

  • Qualitative: Different hues
    • Same value and saturation
  • Sequential: Single hue
    • Increasing saturation or value
  • Diverging: Opposing hues
    • Decreasing saturation toward center

Qualitative: Nominal

Sequential: Ordinal & Ratio

Diverging: Interval

TopHat Question 2

This type of color map would be best suited for which variable?

  • Land use (Forest, Agriculture, Urban, etc.)
  • Temperatures (in Kelvin)
  • Temperatures (in Celsius)
  • Zoning Density (High, Medium, Low, etc.)

Color Choice

Some colors have implicit assumptions depending on the context.

Color Accessibility

About 4.25% of people are colorblind, red-green is the most common. Color Brewer is a great resource.

What Type of Are We Data Representing?

Discrete:

  • Points/lines/shapes
  • Hues

Continuous:

  • Surfaces, contour lines
  • Saturation and value

What is the Measurement Scale?

Nominal:

  • Dashes, shapes
  • Different Hues (colors)
  • Do Not choose colors or sizes that imply a difference in magnitude

What is the Measurement Scale?

Ordinal, Interval, or Ratio:

  • Graduated symbols, line weights
  • Different shades/intensities
  • Do Not choose colors or shapes that imply a difference in category

Visual Hierarchy

The relative importance of features is implied by a maps layout. Our perception is influenced by the order in which we see things and how big / bold they are.

Placement

  • Center first
  • Top to bottom
  • Left to right

Font size

  • Large
  • Medium
  • Small

Intensity (value)

  • Light
  • Medium
  • Dark

TopHat Question 3

Visual hierarchy describes how some hues (colors) are more important than others and how the choice of hue influences our perception of a map.

  • True
  • False

Stylistic Guidelines

  1. Clear labeling to prevent ambiguity and confusion.
    • Minimize assumptions about your audience
    • Proof your map text
  2. Consider if all map elements are necessary.
    • Scale bars, North arrows, etc.
    • Minimize “chart junk”
  3. Use appropriate color schemes.
    • Colorblind friendly
    • High contrast
    • Suited for data type

Stylistic Guidelines

North arrows scale bars

  • North arrow
    • Doesn't work in circumpolar area
    • Not needed for large/familiar regions
  • Scale bar
    • Not always needed if its a large/familiar region
      • Scale text can often suffice
      • Depending on projection (i.e. Mercator), scale will vary drastically across the map

Stylistic Guidelines

North arrows scale bars

  • North arrow
    • Needed if it's not a familiar region or if north is not up
  • Scale
    • Needed if it's a small/unfamiliar region
    • For multiple maps are at different scales
    • Needed if navigation is important
      • i.e., a hiking map

So Many Mistakes!!

  • Poor use of map space
    • Wasted white space
    • Not centered
  • Poor color choice
    • Not colorblind friendly
  • Not all map elements are visible
  • Text/font issues
  • North arrow
    • Placement
    • Size & style
  • Scale bar
    • Wrong units!

So Many Mistakes!!

  • Legend issues
    • Avoid unnecessary text
      • Don't title it Legend
    • Make sure entries are meaningful
      • Get rid of underscores
  • No name / affiliation, date, or data source
    • Be transparent, readers deserve to know:
      • Who made the map (individual / organization)?
      • When was the map made?
      • Where did relevant data come from?

Cleaner Presentation

  • Area of interest takes up most of the map space.
  • Name, affiliation, source.
  • More meaningful legend entries.
  • Proper sizing/placement of map elements.
  • More pleasing color choice, easier for colorblind people to read.

TopHat Question 4

Your maps always need to have a title, scale bar, and north arrow.

  • True
  • False

TopHat Question 5

If you are mapping a region that your target audience may be familiar with, its you should include a north arrow and scale information (scale bar, representative fraction, etc.).

  • True
  • False

Cartographic Principals

These are just stylistic guidelines!

  • Cartography is an art, there are no steadfast rules
    • Just best practices
  • Feel free to play around with styling
    • Just be able to justify your choices
  • Not all spaces “want” to be mapped
    • Sometimes you need to make aesthetic compromises to make an effective map