Geography Reference
In-Depth Information
research. Specification of computational procedures and formulas of both methods
could be found for example in Kuehni (
2003
).
This article focuses on the issue of choropleth maps readability. It aims to
investigate how is the efficient visual distance between classes in the colour
scheme, which allows map users its easy interpretation. Many scientific articles
concerning design of choropleth maps have been written on topics such as colour
perception, rate estimation, optimal classification techniques, and the impact of
enumeration unit geography (Harrower
2007
). Contemporary, much attention is
paid to customization of colour schemes for map users with various color vision
deficiencies (e.g. Kr¨ger et al.
2013
; Culp
2012
; Jenny and Kelso
2007
; Olson and
Brewer
1997
). Another studies are focused on evaluating the efficiency of sequen-
tial color schemes for various purposes (Schiewe and Weninger
2013
; Chesneau
2007
; Mersey
1990
; Gilmartin and Shelton
1989
; Kimerling
1985
, etc.). Harrower
(
2007
) was focused on comparing the efficiency of classed versus unclassed
choropleth maps. Gilmartin and Shelton (
1989
) tested how many classes of
choropleth map are optimal. They also found that humans perform better while
reading choropleth maps with grey lightness continuum, than green or purple. The
great contribution has brought a research activity of C. Brewer, who was develop-
ing colour schemes for visualization both qualitative and quantitative data
(e.g. Brewer et al.
2003
). Quantification of the appropriate colour distance between
classes of choropleth maps is still apparently unexplored part of cartography.
Eventhough colour (and other visual variables) related issues belongs to those
frequently discussed, but also more subtle effects may affect the final map usability.
It is believed that an overall map design could distinctly involve the pleasantness of
map reading. Positioning major design elements should results in a visually bal-
anced map importance (Slocum et al.
2008
). This issue was preliminary evaluated
by Brychtov
´
et al. (
2012
). However no extensive map users
'
oriented research on
how the design can influence the usability of map wasn
t probably done so far.
Both mentioned gaps in the research of maps usability—the effective colour
distance and pleasant map design—are the subject of this presented research.
'
The Experiment
The goal of the experiment was to find out whether particular placement of the
legend could positively or negatively affect the success to search for the informa-
tion and to determine which level of colour distance between classes of choropleth
maps allows the most accurate results. Respondents of the experiment were given a
simple task to determine a value of a depicted area in the choropleth map by
matching its colour with the legend. Results of the experiment were obtained by
analysing the accuracy of respondents
answers and sum of fixation duration in
'
defined areas of interest.
