Cartography: Communicating Spatial Information

Scott BellGIS Institute

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GIS Output and Information Communication

What do we want to communicate?

How can it be communicated?

http://blogs.esri.com/esri/arcgis/2011/10/28/design-principles-for-cartography/Google: ESRI design principles

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What is Happening on a Map? Geography/Space is being simplified

Non-geographic information is being simplified

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Map Types

Let’s see what types of maps we can makeDot densityProportional/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

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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

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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

12Maps created by Tayyab Shah, 2011.

Thematic maps - Choropleth

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Thematic maps – Graduated Symbol

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Cartography Maps as communication Cartographic/Map elements Map Layout Cartographic Semiotics

SymbolsTypography

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Cartography as Communication Maps as visual communication

Special purpose languageGrammar and syntax

Related to graphical communication

Maps as symbolicGeneralizationsrepresentations

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Bertin, J. (1983). Semiology of graphics. Madison, Wis.: University of Wisconsin Press.

Cleveland, William S. 1985. The Elements of Graphing Data. Monterey, CA: Wadsworth.

Schmid, Calvin F. 1983. Statistical Graphics: Design Principles and Practices. New York: John Wiley and Sons.

Schmid, Calvin F. and Schmid, Stanton E. 1979. Handbook of Graphic Presentation, 2nd ed. New York: John Wiley and Sons.

Tufte, Edward R. 1983. The Visual Display of Quantitative Information. Cheshire, CT: Graphics Press.

Tufte, Edward R. 1990. Envisioning Information. Cheshire, CT: Graphics Press.

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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 attention19

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Figure - Ground

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Map Layout Visual Hierarchy

Location on mapSizeProminence

Balance Experimentation Defensibility of each element

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Cartographic Elements Elements found on almost all mapsDistance or ScaleDirectionLegendSources of information and how processed

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Cartographic Elements Selectively use elements

NeatlinesLocator mapsInset mapsIndex maps

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Cartographic Semiotics Theory of signs

Referent and symbol (or sign)

Relationship between the two Cartographers semiotic toolboxVisualOther…

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Symbol Systems Levels of data

Nominal, ordinal, interval, ratio

Feature typesPoints, lines, areas

Symbol systems for each Typography and lettering

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Continuum of Symbols

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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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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