194
nOnTRaDiTiOnaL MaPPing
togram and add color or shading to represent the second variable. This can be done
with rectangular cartograms, as in many atlases, or with topologically correct car-
tograms, which are popular on the Internet. These were especially popular during
the U.S. national elections of 2008 (Plate 10.1). While these are dramatic and eye-
catching, more studies on their effectiveness need to be carried out.
Vermont Population
by County
fIgURe 10.5.
Demers cartogram.
-ISSOURI
#OLORADO
!LASKA
!RIZONA
(AWAII
#ALIFORNIA
.EVADA
.EW
4EXAS
/KLAHOMA
+ANSAS
7YOMING
)DAHO
5TAH
7ASHINGTON
/REGON
-ONTANA
)OWA
3OUTH
)NDIANA
-ISSISSIPPI
!RKANSAS
)LLINOIS
!LABAMA
&LORIDA
/HIO
-ICHIGAN
7ISCONSIN
.EW
$ELAWARE
!LASKA
(AWAII
/KLAHOMA
3OUTH
United States Population Density and Violent Crime
Size of shaded states is
proportional to the state’s
population density.
0-200
201-300
301-500
501-700
Over 700
Rate per
100,000
Source: Statistical Abstract, 2009
fIgURe 10.6.
Bivariate cartogram that shows population density and crime rate.
Cartograms and Diagrams 195
It is also possible to create multivariate cartograms that combine a cartogram
with the principles of the bivariate choropleth.
Distance-by-Time Cartograms
Distance-by-time cartograms have also been called
linear cartograms and
distance
cartograms, but since conventional maps are scaled according to distance units, the
latter is somewhat inaccurate and misleading. These cartograms vary map distances
according to the time needed to travel the real-world distance. This is not a new
concept; some primitive peoples normally made their maps according to a time scale,
rather than a distance scale, because the length of time needed to travel between two
points was of more importance than the actual geographic distance. Today, anyone
who has traveled an expressway or freeway route during light traffic and rush-hour
traffic can appreciate the value of expressing distances in terms of time. Two places
can be exactly the same number of miles from a given point, but one might be 1 hour
away and the other 30 minutes away because of the nature of the roads, amount of
traffic, presence or absence of traffic lights, and nature of the terrain. In fact, on some
freeways the time to get to the next interchange or the airport is posted on flashing
roadside signs.
Two kinds of cartograms are used to represent time; one is linear and shows time
from point to point and may be either directional or not, and the other shows time
from a center point.
Figure 10.7 illustrates a linear cartogram scaled for time along a specific route.
Walking time is used as the scale. It can be seen that uphill segments are longer than
downhill segments. These cartograms are most useful if they show direction of travel;
(B) Potter Pass
8500´
(A) Trail Head
6000´
( )
C
Twin Lakes
6000´½½
C
B
A
Actual Distance by trail 3 Miles
C
C
B
B
A
A
½ hr.
½ hr.
1 hr.
1 hr.
(Direction of travel)
Walking
Time
DIRECTIONAL CARTOGRAM
