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Archive for August, 2007

Perceptual Scaling of Map Symbols

Posted in 09 Map Symbolization on August 28, 2007| 18 Comments »

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What if there was a gap between mapped data and our perception of it?

Buried in the ArcGIS symbolization options for proportional symbol maps is a puzzling check box labeled Appearance Compensation (Flannery) that addresses one gap between perception and data symbolized on maps.

This check box is a vestige of academic cartography’s extensive engagement with psychophysics beginning in the 1950s. Psychophysics relates “matter to the mind, by describing the relationship between the world and the way it is perceived.” Psychophysical studies select specific sensory stimuli and evaluate human perception of the stimuli. Cartographers studied thresholds (what is the smallest type size the average viewer can read?), discrimination (what is the minimum difference between two gray tones required for the average viewer to perceive a difference?), and scaling (how to scale a map symbol so the average user correctly judges the symbol’s value?).

The most studied map symbol was the proportionally scaled circle.

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Map Symbols: Erosion & Flood Control

Posted in 09 Map Symbolization, Map History on August 21, 2007| 4 Comments »

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Dams, bulkheads, arches, ditches, flumes, outlet spreaders, outlet baffles, revetments, riprap, fence, gullies, borings, test pits, siphons, retaining walls, culverts, inlet transitions, jump structure, overfall, tree plantings, sheet erosion plantings, streams, lakes, terraces, ground water, water seepage, water limits, drains, percolators … the language of erosion and flood control in 1930s America.

The above symbols are selected from five pages (full PDF below) in Symbols and Instructions for Maps and Plans, a book compiled and published by the U.S. Department of the Interior Office of Indian Affairs in 1941.

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How Useful is Tufte for Making Maps?

Posted in 06 Map Layout, 07 Hierarchies, 08 Generalization & Classification, 09 Map Symbolization, 10 Type on Maps, 12 Finishing Your Map, Map Books on August 16, 2007| 21 Comments »

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Edward Tufte’s The Visual Display of Quantitative Information (1998, 2nd edition 2001) is a classic book, arguably his best, and certainly a key text in the field of information graphics (which encompasses cartography). I know some cartography courses use the book as a text.

I recall being inspired by the book as a neophyte cartographer back in the late 1990s.

The book looked great: its design communicated the importance of design (when most other cartography and information graphics books were clunky and poorly designed). The tone was serious and high-minded: I was designing information graphics. And I think I absorbed Tufte’s minimalist design philosophy, although cartographic design, at least the way I learned it, was largely minimalist, with no allowance for flourish, fake 3D embellishment, or other chartjunk (or “map-crap” as I call it in the Making Maps book).

While I won’t impugn the importance of lofty inspiration, I did wonder what kind of practical guidelines I could derive from Tufte’s book. You know, specific stuff that would help me to design and make better maps. I sat down one day and made a list of Tufteisms from the book: that list is below.

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Raisz’s History of American Cartography Timelines

Posted in 01 What's A Map?, Map History on August 8, 2007| 2 Comments »

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Harvard’s Erwin Raisz (1893-1968) was one of the 20th century’s preeminent cartographers (bio, bio, bio). Most people know of his landform maps, which are still in print. Raisz was also responsible for a series of atlases and hundreds of maps in books and academic articles.

In a 1937 article for the journal Isis entitled “Outline of the History of American Cartography” Raisz generated a pair of “timecharts of historical cartography” covering key events and individuals in American cartographic history, subdivided into official maps/surveys and private cartography.

Excerpts of the charts, for educational purposes, are linked below.

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