192 nOnTRaDiTiOnaL MaPPing
important than shape for reader acceptance and recognition. However, probably the
most commonly seen cartograms, especially on the Internet, do not preserve shape.
nOnCOnTigUOUs CaRTOgRaMs
Traditional noncontiguous value-by-area cartograms show shapes correctly and either
enlarge or reduce enumeration areas according to the variable represented; adjoining
areas do not touch (Figure 10.3). Although there is usually an effort to place the vari-
ous areas in roughly their correct positions relative to one another, they are separated
by empty spaces. Often, as in Figure 10.3, a true outline of the area is placed around
the enumeration areas. This gives the reader a frame of reference. It allows the reader
to see the region in its entirety in true geographical space and gives an idea of the
gaps, which are considered important in this type of cartogram.
Advantages and Disadvantages. Judy Olson (1976) lists three properties of the
noncontiguous cartogram that make it a useful device:
1. [The gaps between the enumeration units are] meaningful representations of
discrepancies of values.
2. The representation and manipulations involve only the discrete units for which
information is available and only the lines that can be accurately relocated on
the original map appear on the noncontiguous cartogram.
3. Because only sizes of units change, not their shapes, recognition of the units
represented is relatively uncomplicated for the reader.
