Key Points

Introduction to Data Visualization

  • Data visualization turns numbers into positions, lengths, areas and colors that people can compare quickly.
  • Exploratory figures help you understand your data; explanatory figures communicate one message to others.
  • Correct data can still mislead through truncated axes, the wrong chart type or poor color choices.
  • Choose the chart type from the question, label everything, and keep scales honest.
  • Python and QGIS are free tools that cover charts, maps and cartographic layouts.

Cartography Checklists

  • Decide the audience, message and medium before designing a map.
  • State the message in the title and show only the data that supports it.
  • Rates and counts answer different questions; choose deliberately.
  • Design choices such as palette and classification change what readers believe.
  • Review every map against a checklist before sharing it.

Fundamentals of Map Design

  • A map layout needs a title, legend and source, plus a scale bar and north arrow when they help.
  • Sequential, diverging and categorical color schemes match ordered, centered and unordered data.
  • Every projection distorts something; use equal area projections for thematic maps.
  • Choropleth maps need rates; show counts with proportional symbols or dots.
  • The classification method changes the pattern a map shows; use the same breaks to compare maps.

Cartography in Python

  • Style each layer by its role; the subject is strong, context is quiet
  • Label sparingly, by rule, with halos; italics for areas and water
  • Use quiet basemaps and keep their attribution; scale bars need a projected CRS
  • A locator inset shows where the map is; small multiples compare, with shared breaks only for comparable values
  • Export PDF for print and PNG at 200 to 300 dpi for screens, and check the exported file

Cartography in QGIS

  • Style each layer by its role; the subject is strong, context is quiet
  • Convert Graduated to Rule-based to add a “no data” rule; label by rule with a text buffer (halo)
  • A second map item with an Overview makes a locator inset; Lock layers keeps each map’s content
  • Scale bars need a projected CRS; small multiples share classes only for comparable values
  • Export PDF for print and PNG at 200 to 300 dpi for screens, and check the exported file

Accessibility in Map Design

  • About 1 in 12 men of Northern European ancestry has a red-green color vision deficiency.
  • Vary lightness, not just hue, so classes stay distinguishable for everyone.
  • Use colorblind-safe palettes such as viridis, cividis, Blues or ColorBrewer’s colorblind safe schemes.
  • Add a second cue (labels, patterns, shapes) when categories matter.
  • Test with a simulator such as QGIS Preview Mode, and write alt text for maps shared online.