Geography 353 Cartography and Visualization

...to Geog 353 Main Page and Course Description
...to Geog 353 Syllabus
...to Geog 353 Course Schedule and Lecture Outlines
...to Geog 353 Laboratory Information and Student Projects


Geog 353 Lecture Outline: Color on Maps
Update: 10/5/16

We will review chapter 12 (Color on Maps) from the Making Maps book. Additional information and examples can be gleaned from the material below.







Introduction

Color is fundamentally important to cartography and fundamentally confusing


Mark Monmonier: Color as a cartographic quagmire: why?

"I do not advance that the face of our country would change if the maps which Philadelphia sends forth all over the Union were more decently colored, but certainly it would indicate that the Graces were more frequently at home on the banks of our lovely rivers, if the engravers were able to sell their maps less boisterously painted and not as they are now, each county of each state in flaming red, bright yellow, or a flagrant orange dye arrayed, like the cover produced by the united efforts of a quilting match. When I once complained of this barbarous offensive coloring of maps, the geographer assured me that he would not sell them unless bedaubed in this way; 'for, said he, the greatest number of the large maps are not sold for any purpose of utility, but to ornament the walls of barrooms. My agents write continually to me to color high.' This reason was given me by one of the first geographers of the United States, who has himself a perfectly correct idea of the tasteful coloring of maps."

--from Francis Lieber, "On Hipponomastics: A Letter to Pierce M. Butler," Southern Literary Messenger 3 (5) (May 1837): 297-300.





Discussion of color and cartography:



1. An Introduction to Basic Color Terms and Perception

1a. How Do We See Colors?

Color perception issues: the sensing and understanding of color: three elements


1. Characteristics of the light source




2. Characteristics of the surface of the map




3. Characteristics of Human Color Perception

Humans are sensitive to a small band of electromagnetic energy which is called visible light


Using color for cartographic design requires an understanding of how people perceive color



Human color perception consists of...

1. hue: names for psychological experiences of particular electromagnetic wavelengths



2. value (lightness): perceived lightness and darkness




3. saturation (chroma): amount of pure hue in a color relative to neutral grey




1b. How Do We Create Colors?

Color production issues

We create colors in ways that are often different from the way we perceive colors


Color specification systems: schemes which organize and help produce different colors. There are numerous ways to organize and produce colors, all of which are used by cartographers and graphic designers.

Most color specification systems provide some kind of unique identifier for each different color in the system: they help specify unique colors for printing and for computers

Three categories of color specification systems you need to be familiar with:


A. Perceptual Color Systems: based on how humans see colors


Munsell Color System: a three dimensional color space which is based on hue, value, and chroma/saturation; each color chip is differentiatable by the average viewer




B. Predefined Color Systems

Pantone Matching System: series of preselected colors which are available to commercial printers; you select a color and the printer obtains the correct ink mixtures


Use Pantone when you are going to have a map printed by a commercial printer. Also provides a diverse palette of colors.





C. Process Color Systems: the use of varying amounts of 3 primary hues to produce all other colors

Different for color production in printing vs on computer screens

C1. Process color systems for printing (commercial printers)


You can get a broad range of colors (hue, value, chroma) based on varying combinations of cyan, magenta, and yellow



Color Primaries


Cyan, magenta, and yellow are called the subtractive primaries


Subtractive Primaries are the most common system used in printing


Problem: if you want black you can get it by combining 100% of cyan, magenta, and yellow, but resulting color is a very dark brownish color



C2. Process color systems for computer screens


RGB: red, green, blue are called the additive primaries

You can get a broad range of colors (hue, value, chroma) based on varying combinations of red, green, and blue


Additive Primaries the most common system used in creating color on computer screens (and computer printers)


Color specification in HTML: Hexidecimal Color Specification System


Many excellent Color HTML sites on the WWW:



2. The Complexity of Color Use

2a. Color Interacts with its Environment

Simultaneous contrast: the appearance of any color in a display depends on the colors that surround it


This is an artifact of the way our brain interprets color

Carefully pre-selected colors (selected independently of each other) will often look different when combined on a map

Little we can do about it except to carefully evaluate the way colors interact together on a map




Successive contrast: colors are modified based on the order in which they are seen; related to simultaneous contrast





Visual acuity: monochromatic backgrounds (one hue) make it easier to pick out colors than mixtures (such as brown)





Advance and retreat: perceptual phenomena whereby reds seem to advances (stand out more) and greens and blues seem to retreat (fall back more) in the visual plane


Why does advance/retreat happen? Our eye physically adjusts itself a bit when perceiving longer wavelength reds and this seems to produce this effect; very subtile




Individuality of Hues



Implications:



Color location, size, and shape: colors will seem to vary as their location, size, and shape varies




Implications of all of these issues: color cannot be selected independent of its context




2b. Changing External Conditions Affect Perception

The appearance of any color in a display varies as the lighting conditions of the room the display is in change



Color varies as the settings of one computer monitor vary

Implications:




2c. Physiological Differences among Individuals

The appearance of any color in a display varies based on who is viewing it

Young children (less than 5 yrs old) seem to understand only a limited set of hues, and have difficulty arranging different color values in any kind of order


Older people are less sensitive to color and need brighter (saturated) colors


Color blindness in 3% of females and 8% of males (red and green look same)




...finally: color use is complex because...


2d. Color has Symbolic and Emotional Connotations

The meaning we get from different colors varies


Our culture has conventional meanings for different colors


Implications: use these conventions to match phenomena with color




3. Color Hue and Color Value and Choropleth Maps

"Appropriate use of color for data display allows interrelationships and patterns within data to be easily visualized. the careless use of color will obscure these patterns."


Brewer's guidelines are derived from two sources


In essence: we want color use to be as intuitive as possible




Brewer's Color Guidelines


General rule of thumb: hue for qualitative differences, value (lightness) for quant/ordered




1. One Variable Color Schemes


1a. Qualitative Schemes: qualitative difference in data



1b. Binary Schemes: qualitative difference in data



1c. Sequential Schemes: some order or sequence in the data (quantitative)



1d. Diverging Schemes: importance focused on a mid point and variations out from that midpoint



Two and Three Variable Color Schemes





Summary

An overview of the many issues surrounding the use of color to represent information

1. An Introduction to Basic Color Terms and Perception

How Do We See Colors?


How Do We Create Colors?


2. The Complexity of Color Use


3. Color Hue and Color Value and Cartographic Design

Brewer's scheme whereby the perceptual dimensions of color correspond to logical organization of the mapped data

Color misused more than other visual variables

Remember: variations and changes in color should mean something

Avoid creating your own cartographic quagmire!




E-mail: jbkrygier@owu.edu

...to Geog 353 Main Page and Course Description
...to krygier teaching page.
...to krygier top page.

OWU Home
OWU Geology and Geography Home