SOAPBOX
Web-Based Mapping—Now Possible without Troublesome
Cartography!
Martin von Wyss
I t’s not a new tale, really. Technology
simplifies a task and, in the process, puts a craft in the
hands of the creative if somewhat unskilled. Though more
manuscripts exist today since word processors made it
simple for the amateur to put ideas down in a neat
document, the budding novelists still need editors.
Similarly, just because publishing maps on the Web is
easy, we shouldn’t ignore map design.
The Modern Language Association (MLA) of New York
recently published its Language Map (http://www.mla.org/census_map).
It is terrific, and one of the best of the many
interactive, Web-mapping applications based in GIS. The
Language Map contains fantastic but complex data, and
makes them understandable by an interactive data viewer.
Unfortunately, map design was given hardly a thought. This
seriously undermines the effectiveness of the map.
The Language Map is a choropleth map, or one that
uses map area to show both land area and data. Such maps
shouldn’t distort either land area or shape, but the
Language Map, unfortunately, uses a rectangular map
projection that distorts the states’ shapes. Such
rectangular projections are the default in most mapping
software packages, probably because they are
computationally easy and maybe also because our computer
windows are rectangular. One of these rectangular
projections, the Plate Carée, might usurp the Mercator
projection as the most common and the most commonly
misused projection. While even television’s The West
Wing has weighed in on misuses of the Mercator, the Plate
Carée is not discussed often. When it is, it is often
incorrectly referred to as “unprojected” or as
“geographic coordinates.” How could the nearly
spherical earth be represented on a flat piece of paper or
computer monitor if it wasn’t projected? Or how can
something on a map not be geographic?
Although it is seldom mentioned by name, Plate Carée
is common because it displays latitude and longitude units
as having equal lengths in both the north-south and
east-west directions. Since this unique property makes the
math easy, many GISs have Plate Carée as their default.
National Geographic’s “Map Machine” and the U.S.
Department of Housing and Urban Development’s
“Enterprise Geographic Information System,” both made
in partnership with ESRI, use Plate Carée. This
projection and its areal distortion are sadly ubiquitous
for no other reason than it simplifies data structure and
expedites screen redrawing. This projection and other
rectangular projections are rarely appropriate for a map
of the United States, such as the Language Map.
The map designers could have left the viewer with a
more meaningful and more accurate representation of the
information had they normalized the data (Figure 1). Since
the MLA chose to show absolute numbers instead of
densities of people, the Language Map gives inappropriate
emphasis to sparsely-populated counties that are large in
area. Figure 2 shows that most of the nation’s 178,014
Navajo-speakers reside in four counties in the southwest.
The Navajo-speaking population is cartographically
over-represented because its concentration, depicted by
the pink areas, covers about 1.2% of the map, whereas that
population only makes up less than a hundredth of a
percent of the total U.S. population on the map.
Similarly, the proportion of people who speak a certain
language would be more informative than raw numbers. Three
interesting but discrete facts have been lumped together:
that these counties are large in area, that their
population is sparse, and that the population has a high
proportion of Navajo-speakers. Through muddled design, the
unique meaning has been lost.
A third major problem with the map is that the
color scheme is inappropriate. Although GIS software often
cleverly promotes sensible and intuitive color schemes,
bright, vivid colors can seduce those for whom information
comes second to glitz. The result turns map reading from
an informative, easy task, into a garish exercise in
comparing the map to the legend (Figure 3).
Perhaps as the number of Web maps increases, so
will readers’ sophistication. But just as Microsoft Word
doesn’t yet have a button that generates the perfect
poem, the publishable paper, or the best-selling novel,
Internet map software needs cartography to make honest,
meaningful, easily understood maps.
About the Author
Martin von Wyss of vW Maps, Inc. (www.vwmaps.com) has more than ten years of experience in
map making and cartographic consulting. He has produced
maps for a variety of different media, including books,
magazines, software, and a big rock in a park.
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