MAPS & JUDGMENT

1. MAPS & JUDGMENT Steps toward cartographic literacy

2. Projections • Every map employs some kind of projection to transform spherical surface to flat surface • Choice of projection reflects priorities of cartographer in regard to preserving one of the following (or compromising between all) • Area • Distance • Direction • Shape • Read the Introductory section in your atlas (this is required reading!)

3. Mercator projection Why did my plane from Paris go so far out of the way to get to Chicago?

4. Mollweide Projection Maybe it didn’t go too far out of the way…

5. Azimuthal projection (north pole) That explains it! Remember that every projection is a distortion. How is this projection distorted?

6. Judgment is inevitable when making maps • All maps involve decision-making process • There is no “natural” way to draw a map • Maps are not reflections of reality but selections of reality • Maps can be analyzed and critiqued just like literature to determine what the cartographer believed and thought about the world, and his/her values, beliefs, objectives, etc. (J.B. Harley, John Pickles, etc.)

7. Who might have made this map and why?

8. Medieval “T&O” map What common words in the English language reflect this tradition of mapping? • Orientation • Oriented

9. Thematic Maps • Thematic maps represent one or two variables (population, ethnicity, income, language, religion, etc.) in map form • The “language” of thematic maps is quite varied, and involves the use of color, shape, pattern, light and dark, etc. • Thematic maps serve two main purposes: • Analysis of data • Presentation of data

10. Map with pie chart callouts What are the strengths and weaknesses of this cartographic language?

11. Choropleth map What are the strengths and weaknesses of a choropleth map?

12. Cartogram and choropleth A cartogram is a boundary map in which the areas are distorted systematically: every partition’s area shows its value for a particular variable

13. Isoline map of population Why use an isoline map for population rather than a choropleth map?

14. Choropleth maps From A to Z

15. Choropleth maps • Tremendously common and useful • Use some existing system of boundaries (countries, states, counties, voting districts, etc.) • Group data into 2 or more levels or classes using slicing values • Show spatial variation of one or two variables at a time by using color, shades of grey and/or patterns

16. Percent of Population White (not Hispanic)

17. Percent of Population White (not Hispanic)

18. How can such different looking maps show the same variable? • Cartographic reasons • Different slicing values • Different levels of spatial aggregation • Geographical reasons • Uneven distribution of minorities at the state scale as well as at the national scale • Concentration of minorities in cities, particularly in northern states

19. Different ways of “slicing” data • The Data {42, 50, 55, 57, 61, 77, 79, 97} • Equal interval • Three classes based on range 40 to 100 • {42, 50, 55, 57} {61, 77, 79} {97} • Quantile • Quartiles (lowest 1/4 of observations, next 1/4, …) • {42, 50} {55, 57} {61, 77} {79, 97}

20. Different ways of “slicing” data • Natural breaks • {428505552574616772791897} • {42} {50, 55, 57, 61} {77, 79} {97} • Standard deviations • Mean = 64.75, Std. Dev. = 15.977 • {42} {50, 55, 57, 61} {77, 79} {97}

21. Natural Breaks

22. Equal Interval

23. Quintiles (quantiles based on division into 5 classes)

24. Which map would be preferred by each of the following users? • The ACLU • The KKK • A geographer studying the relationship between ethnicity and poverty • A spokesman for the Georgia branch of a charitable assistance association targeting minorities

25. Not very useful this way • Generally it helps to re-order the data

27. quartiles: what is 52 ÷ 4 ? What if you wanted to use quintiles?

28. How informative would “natural breaks” be in this case?

29. Problems with choropleth maps • Make it easy to slant data to suit the cartographer’s purpose (by adjusting the slicing values) • Create the illusion of rapid breaks whereas data varies continuously and gradually in the real world • Allow small areas (like major cities) to overwhelm the data of large regions (like states)

30. Mapping inequality in Africa • Mapping economic inequality • Variable used: GINI index

31. GINI index measures economic inequality in a society 100% = completely unequal 0% = completely equal

32. Can you identify the classification schemes? Equal Interval 28-37.99 38-47.99 48-57.99 58-67.99 68-77.99 Quantiles (Quartiles) 32 entries ÷ 4 = 8 4 groups of 8

33. Can you identify an observation that “jumps” two classifications?

34. Can you think of a scenario with: • Two different map users (think in terms of organizations and professionals) • Opposite judgments of what is the “best” map for their purposes? South Africa South Africa

35. What would you guess… ? Source: Wikimedia commons

36. Process Maps How can you map a process?

37. Map with pie chart callouts To see the process (growing American dominance in the movie theater) you have to visually compare each pair of pies

38. Expansion of the EU To see the process (expansion of the EU) you have to know what color comes first, second, third, etc.

39. Religious diffusion To see the process (religious diffusion) you must follow the arrows

40. Mei-Po Kwan To see the process (human movement) you must follow the time-space path from the bottom of the lower blue line to the top of the upper blue line

41. Mei-Po Kwan

42. Paul Adams

43. Charles Joseph Minard’s map of the disastrous Napoleonic campaign in Russia (1812)

44. Questions • Why use an isoline map instead of a choropleth map? • Why use a choropleth map instead of an isoline map? • What kind of map is unbiased? • What kind of map reflects the interests, intent, and biases of the mapmaker? • What are some problems with choropleth maps? • What are some processes that people have managed to map? • What are some cartographic ways of showing change through time?