A lot of ink gets devoted to questions of visual hierarchy but, at its core, it is nothing more than the idea that the important part of a map should be more visible than the less-important parts. Introductory texts tend to illustrate the concept with wildly distorted examples in which the title of a map document, for example, occupies more of the page than the map itself. Beyond obvious cases like that, establishing an appropriate visual hierarchy can be tricky.
Here’s a black and white map of a county park in Kansas City. It’s intended to guide readers to some interesting architectural features in that park and to help the reader understand the historical and cultural significance of those features.
It’s a good start, but the lake is a bit vague. And, while I don’t like to add purely decorative elements to a map, this one needed a border to hold the image together. Borders — more technically, a neatline — are a bit controversial. On one hand, they are a standard design element of many maps. On the other hand, there is a notion in graphic design, advanced emphatically by the revered scholar of design Edward Tufte, that one should strive to maximize the use of graphical elements that communicate information and avoid the use of elements that are decorative. A border communicates very little; the map reader is perfectly capable of telling where the map ends without a box to define that border. Yet there is a small amount of value in marking the full extent of a map, if only to assure the reader that nothing was cut off. As a bit of a compromise, I added a very thin dashed border.
It’s a reasonably effective map. It identifies the places of architectural interest, gives the viewer a thumbnail sketch of the features and provides some indication of where in the park they are located. But there is something just a bit muddy about the design. As a thoughtful colleague, the cartographer Liz Thomas, immediately saw what I did not: there was no meaningful visual hierarchy to the map. Everything was of equal visual impact, so nothing stood out. Instead, it was a bit of a visual jumble. So, following Liz’s advice, I gave more visual weight to the illustrations of areas of architectural interest and less to the background map.
The use of a border that is purely decorative still rankled, so I modified the border to turn it into a calibrated measure of distance — denominated in kilometers, meters, miles and feet — essentially a scale bar that continues around the entire map.
The calibrated border is an adaptation of the border used on nautical charts published by the National Oceanic and Atmospheric Administration. These charts use a border marked in degrees and minutes, a centuries-old system of identifying locations anywhere on the Earth’s surface. [It’s the same system that is often referred to as “GPS coordinates,” as though latitude and longitude did not exist prior to the public deployment of GPS in 1993.] Experienced users of these charts often use the distance between the one-minute ticks on the chart border to measure distances on the chart, taking advantage of the fact that one minute of arc of latitude is almost exactly one nautical mile.