Geography Reference
In-Depth Information
“The more of a phenomenon, the darker the color”: This type is based on
Imhof
s “the higher, the lighter” example, resulting in a presentation that appears
three-dimensional. In thematic cartography this is usually inverted.
Modified spectral schemes: Spectral schemes are popular in visualization—
61 % of the papers of the IEEE Visualization Conference from 2001 to 2005
without medical figures made use of the spectral scheme (Borland and Taylor
2007
)—nevertheless they are to challenge:
Perceptually [
'
] this scale does not appear linear. Equal steps in the scale do not
correspond to equal steps in color, but look instead like fuzzy bands of color varying in
hue, brightness and saturation. When mapped onto scalar data, this colormap readily gives
the user the erroneous impression that the data are organized into discrete regions, each
represented by one of the rainbow colors. This can lead the user to infer structure which is
not present in the data [
...
] (Bergman et al.
2006
, p. 119).
If only parts of the spectral scheme are used and modified—for example
saturation and lightness balanced—it can be an interesting option for some use
cases with a big data range or a logarithmic scale, as our practical experience
showed.
...
Color Design Aspects for Digital Maps
Color Design Guidelines
Levkowitz (
1996
, p. 97) defines general guidelines for color design: Colors of a
scheme should:
1. “preserve the order of the original values”;
2. “convey uniformity among values they are representing, and representative
distances between them”; and
3. “create no artificial boundaries that do not exist in the original data”
The first rule is established in cartography and basis for sequential and diverging
schemes. The other two rules are reasonable, but it is difficult to put them into
practice, especially for non-cartographers. Especially representative distances is an
aspect that has not been further defined in cartography, therefore it is the aim to
contribute to this discussion (refer to guideline 2). Moreover, Levkowitz
s guide-
lines focus on the data and neglect the complexity of perceptional and user issues
that go along with color. Color is a physical stimulus that causes physiological as
well as psychological reactions. In respect thereof we describe design guidelines
that help to develop effective color schemes:
'
1. To represent partially or fully ordered data colors should build a harmonical
hierarchy (Jones
2010
, p. 46), i.e., lightness
and
saturation should in- or
decrease systematically at one end of the scale. Harmonical hierarchy is
achieved in single-hue sequential schemes, or multi-hue sequential schemes
