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On This Page:  •  Monochromatic Charts •  Multicolor Charts

  This page discusses how color is used in existing paper maps and charts for aviation and some of the issues in adapting them for electronic display.

Maps and charts are particularly interesting as a resource for study of color usage in information displays due to the age of the medium. Cartographers have an extensive historical practice to draw upon, and the best modern maps are highly evolved. While some of this color expertise is explicitly available in cartography textbooks, other aspects are implicit in successful modern maps.

Aviation charts have very high data densities, and most are intended for use by pilots while airborne, often in single pilot aircraft. Safety considerations and high cognitive workload make excellence in design a requirement rather than a luxury. Many of today's paper charts and maps are remarkably complicated and approach the limits of the medium. Efforts are well underway to replace the paper in the cockpit with electronic versions. The different capabilities of printed paper and current electronic displays will require some redesign of the graphic content.

Monochromatic Charts Back to the top of the page.

Many of the documents in the cockpit are printed in a single color of ink, usually black, with grays from halftones. Examples include charts and tables giving details of procedures in terminal areas and at airports and maps of runways and taxiways. The graphics designs manage legibility and attention allocation by mature cartographic methods. Contrast polarity is dark symbols on light backgrounds. Backgrounds are mostly white, with some shading of area data, such as bodies of water, terminal buildings, and runways. Area data are also occasionally patterned. Saliency of symbols and alphanumerics is manipulated by font size, type style (boldface, italics), and luminance contrast (gray vs. black on white).

Monochrome airport diagram
Larger Image New Window.

Closeup of a monotone airport map. Larger Image New Window.

Multicolor Charts Back to the top of the page.

Multicolor charts and maps are also in widespread use in aerospace applications. In the simpler designs many charts use chromatic color for grouping, labeling, and popout of symbols. In more complex designs, some charts also use chromatic color for labeling of several altitudes of terrain. In the most complicated area and sectional charts color-labeled symbology is superimposed on multicolored shaded terrain. The shaded backgrounds use most of the available luminance range of the medium, making addition of any further data a design challenge.

Arrival Chart: This is a sample from an arrival chart for an airport in the Rocky Mountains. The design codes five levels of terrain by varying saturations and lightnesses of tan. The important navigation symbology is printed in dark colors, giving it high luminance-contrast (and high salience) against the light colors of the terrain data. Font size and style are also used to manipulate saliency and labeling. Closeup of an multicolor arrival chart for a Rocky Mountain airport Larger Image New Window.
Sample from the NOAA San Francisco sectional chart  Larger Image New Window.

Sectional Chart: This is a sample from the NOAA San Francisco sectional chart. These remarkable charts have very high data densities, probably approaching the limit for use in the cockpit.

Color is just one of several graphic variables used to achieve the visual hierarchy of the information. The color design restricts the area variables (terrain elevation, water) to a narrow range of high lightnesses by assigning them unsaturated colors. Lines, symbols, and alphanumerics are assigned darker colors, with more important information at higher luminance contrasts. Further distinctions among the high luminance contrast data are achieved by varying symbol sizes and stroke widths.

Limits of area data coloring
. In this magnified (2.7:1 on an 87 dpi display) detail from the San Francisco Regional Chart the terrain slopes gradually and the altitudes are moderate. Consequently the shading and color labeling remain fairly light. This gives the black text high enough luminance contrast to be quite legible.

Magnified detail from the San Francisco Regional Chart

Magnified detail from the San Francisco Regional Chart


In this second detail (same magnification) from another region of the same chart the color labeling and shading of the terrain are darker due to the higher altitudes and slopes. Even at this magnified size the black text is harder to read. Note the subtle text outlining; the shading is turned off in the vicinity of the lettering.

The symbols and alphanumerics would be more legible if the outlining were lighter. Better still, the luminance contrast of the terrain-color / 3D-shading scheme could be reduced by using paler colors. Even very pale shading can give a strong 3D impression.
More about outlining in Last Resorts.

Related Topics:
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Designing a Graphics Page (Checklist)
go to this page Choosing Background Colors
go to this page Designing with Luminance Contrast
go to this page Color Graphics Concepts

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