SOLVING GEOSPATIAL TASKS IN 2D AND 3D VISUALIZATIONS OF MAPS - Information Visualisation: Techniques, Usability and Evaluation - page 232

et al. [16] showed that strong 3D cues are important, and that stereoscopic
cues did not have any additional enhancing effects in the presence of
motion cues. These results suggest that dynamic visual cues in 3D
visualizations might be more important than stereoscopic cues. This
assumption is further supported by [17] in a study on path tracing tasks,
where stereoscopic cues added alone to weak 3D visualizations were
found to have no effect, whereas the addition of motion cues did.
In the context of visualizations of maps and scalar information related
to map positions, few formal evaluations of 3D and 2D visualizations
exist. In a recent study, Bleisch et al. [18] compared users' discrimination
of bars that were presented either on a 2D map or in a 3D terrain map. No
differences in time and correctness were found. Similarly, no significant
effects were found in a study comparing 2D and 3D visualizations of
spatio-temporal information [11].
This chapter describes two user studies previously carried out by the
author to investigate users' performance in solving fundamental spatial
assessment tasks in maps. They compare different forms of 2D and 3D
map presentations according to the notion introduced above.

Experiment I: Estimation of distances in 3D tilted maps

A first experiment, which was originally published in [19], aims to test the
hypothesis that for a strong 3D presentation, accurate assessment and
effectiveness are not affected for tilt angles larger than 35 ͼ and up to 65 ͼ
out of the fronto-parallel plane.

Task and stimuli
Participants in this experiment had to identify the closest pair of positions
out of a number of marked positions on a map. The visual stimulus
consisted of a 2D map of square shape with an edge length of 20.0 cm. On
this map, n =15 randomly chosen positions were marked with red dots (see
Fig. 12.3). The number of possible distances to be evaluated is

2

n n

n
k

¦

k

2

1

or .

Each trial (i.e., repetition of the experiment) comprised the assessment
of 25 different stimuli. The stimuli had different distributions of the
positions, while the map was chosen to be the same in all stimuli. The
degree of difficulty for this task is potentially affected by the number of
locations to choose from. In pre-tests, this number was determined to be