Cartography: Communicating Spatial Information Scott Bell GIS Institute

2 GIS Output and Information Communication What do we want to communicate? How can it be communicated? 10/28/design-principles-for- cartography/ Google: ESRI design principles

3 What is Happening on a Map? Geography/Space is being simplified Non-geographic information is being simplified

4 Map Types Let’s see what types of maps we can make Dot density Proportional/graduated symbol choropleth

Dot Density Maps Portraying numeric/count data with dot density Dots coincide with enumeration area DO NOT represent location of observation Dots represent a CONSTANT quantity Generalization is associated with aggregation Use with quantities of observations 5

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Proportional/Graduated Symbol Symbol size varies in proportion to attribute value “proportional” implies a continuous range of symbol sizes Also called Graduated Symbol and Variable Symbol “graduated” implies symbol size is associated with a range of attribute values Used with ratio data that has a range of values absent of outliers 8

11 Choropleth Maps Portraying statistical data with area symbols Area symbols coincide spatially with and represent data values for enumeration zones Features in the same class should be similar and should be symbolized similarly Features in different classes should be dissimilar and should symbolized differently

12 Maps created by Tayyab Shah, Thematic maps - Choropleth

13 Thematic maps – Graduated Symbol

14 Cartography Maps as communication Cartographic/Map elements Map Layout Cartographic Semiotics Symbols Typography

15 Cartography as Communication Maps as visual communication Special purpose language Grammar and syntax Related to graphical communication Maps as symbolic Generalizations representations

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17 Bertin, J. (1983). Semiology of graphics. Madison, Wis.: University of Wisconsin Press. Cleveland, William S The Elements of Graphing Data. Monterey, CA: Wadsworth. Schmid, Calvin F Statistical Graphics: Design Principles and Practices. New York: John Wiley and Sons. Schmid, Calvin F. and Schmid, Stanton E Handbook of Graphic Presentation, 2nd ed. New York: John Wiley and Sons. Tufte, Edward R The Visual Display of Quantitative Information. Cheshire, CT: Graphics Press. Tufte, Edward R Envisioning Information. Cheshire, CT: Graphics Press.

18 Designing Maps Well Clarity and Legibility Figure – Ground Balance Visual Hierarchy Contrast Audience, Venue, Intent, and Format

Clarity and Legibility Easy to read Symbols, legends, themes Colors, patterns, etc. used to differentiate distinct symbols and elements Individual elements should be larger than required for regular vision Focus of attention 19

20 Figure - Ground

21 Map Layout Visual Hierarchy Location on map Size Prominence Balance Experimentation Defensibility of each element

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23 Cartographic Elements Elements found on almost all maps Distance or Scale Direction Legend Sources of information and how processed

24 Cartographic Elements Essential Elements that are sensitive to context Title Projection Cartographer Date

25 Cartographic Elements Selectively use elements Neatlines Locator maps Inset maps Index maps

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27 Cartographic Semiotics Theory of signs Referent and symbol (or sign) Relationship between the two Cartographers semiotic toolbox Visual Other…

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29 Symbol Systems Levels of data Nominal, ordinal, interval, ratio Feature types Points, lines, areas Symbol systems for each Typography and lettering

30 Continuum of Symbols

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34 Typography and Text Content and Form “Colonies controlled or ruled by the Spanish Empire on the eve of the Spanish-American War” or “The Spanish Empire in 1898” Sans serif vs. variable font styles

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36 Choropleth Mapping Portraying statistical data with area symbols Area symbols coincide spatially with and represent data values for enumeration zones Other quantitative maps proportional circle maps dot maps Isarithmic maps value-by-area cartograms

37 Choropleth Maps One type of Thematic Map Requires data generalization Generalization for choropleth mapping is synonymous with classification Differentiate between categorical and numerical data … remember nominal, ordinal, interval, and ratio

38 Classifying Categorical data Features in the same class should be similar and should be symbolized similarly Features in different classes should be dissimilar and should symbolized differently

39 Classifying Numerical data Two primary considerations: Number of classes Division of classes Changing the number of classes can dramatically change the appearance of your data

40 Division of data Determining classes that will represent breaks in the data Some schemes take into acct. the internal (statistical and non-statistical) character of the data Some schemes are arbitrary and/or external

41 Exogenous schemes: class boundaries defined by criteria external to distribution of data Arbitrary schemes: class boundaries are set by arbitrary criteria Ideographic schemes: class boundaries defined by the shape of the data distribution Serial schemes: class boundaries are defined by statistical or mathematical functions Unclassified Schemes

42 7 Design Considerations know your subject decide on an appropriate scale decide on volume of data to be presented (esp. # of areal units) data preprocessing (intensive data) data classification areal symbolization legend design