Geography Reference
In-Depth Information
Experimental Design, Conditions and Participants
The experiment consists of 46 stimuli which are characterized by 6 different legend
positions I to VI (see Fig.
1
) and 8 colour schemes with different colour distance
step between classes. Five of these schemes have equal colour distance steps
between their classes—the lightness of their colour decreases by the same amount
of colour distance (
2, 4, 6, 8 or 10) through the whole scheme (see Table
1a
).
Next three schemes were designed and tested based on the first phase of evaluation
of experiment, which is described further. Those schemes are designed so the steps
between classes are not homologous. The sequence of colour distance steps con-
form to values
E
00
¼
Δ
E
00
4-8-10-8-4, 6-8-10-8-6 and 4-6-8-10-12 (see Table
1b
). Each
choropleth colour scheme is compounded by 6 classes A to F (A refers to the
lightest, F to the darkest shade of the scheme).
All colour schemes are made of lightness continuum of green. In order to keep
the endurable length of the experiment no other hue continua were tested.
The experiment was carried out under controlled conditions in the laboratory at
Department of Geoinformatics, Faculty of Science, Palack´ University in Olo-
mouc, which is equipped with a low-frequency contactless eye-tracker SMI RED
250 with a sampling frequency 120 Hz. Stimuli were projected on 23 “LG Flatron
monitor IPS231P”. Stimulus size was 1,920
Δ
1,080 px. Design of the experiment
was prepared in SMI Experiment Center
(SensoMotoric Instruments
2013
).
Detection of fixations was performed through the SMI BeGaze
™
(SensoMotoric
Instruments
2013
) using ID-T (dispersion threshold algorithm). Dispersion thresh-
old was set to 50 px and a minimum length of 80 ms.
The experiment was attended by 35 respondents [19-35 years; 19 males and
16 females; 18 experts in the field of cartography and 17 novices (based on self-
evaluation)]. Prior to projecting experimental stimuli, participants were subjected
™
ABCDEF
V
I
III
A
B
C
A
B
C
D
E
F
D
E
F
ABC
VI
II
IV
A
B
C
D
E
F
DEF
A
BC
DEF
Fig. 1 Six groups of stimuli with different position of the map legend: (
I
) up; (
II
) down; (
III
) left;
(
IV
) right; (
V
) vertically split; (
VI
) horizontally split
