Cartographic and Cognitive Perspectives on Ambulance Dispatch Displays - Geospatial Visualisation - page 74

Fig. 4 The NRCC map display and superimposed ambulances, ambulance stations etc. Notice
the clutter on the left hand side (from Hayes 2006 )

5.3 The Experiment

An experiment was performed using snapshots of the NRCC map display, iden-
tified as a source of data overload, and therefore visual clutter adding to perceived
complexity (see Fig. 4 ). The aim for this study was to examine how appropriate
information representations can improve the dispatcher's performance on the
dispatch task (Hayes et al. 2006 ). A Multi-Layered Display (MLD) was used in
this (Fig. 5 ), a novel technology consisting of two overlapping LCD (Liquid
Crystal Displays) separated by a 10 mm thick transparent Perspex layer. A copy of
the actual map-based display used by the emergency ambulance controllers was
developed and then re-designed so that key pieces of information needed by the
dispatch task were placed on the transparent front layer of the MLD, while con-
textual information such as the map and location of secondary medical resources,
were presented on the rear LCD (Fig. 5 ). Such information layering offering a
contextual grouping by depth is another example of the PCP at work. Also, the
operator's cognitive load is believed to be lessened by not having to turn infor-
mation on and off, adding to the decision making time.
The experiment itself involved 40 participants with normal colour vision. It was
designed

as a between subjects 2 9 4 (single Layered Display SLD/