Geography Reference
In-Depth Information
14
Making Uncertainty Usable:
Approaches for Visualizing
Uncertainty Information
Stephanie Deitrick and Robert Edsall
School of Geographical Sciences, Arizona State University
14.1 Introduction: the need for representations
of uncertainty
Not long ago, we began the creation of an atlas of cultural geography of the Phoenix metro
area. In one particular meeting with students for feedback on some of the draft maps, one
student we noticed was concentrating very hard on a map of movie theatres in the region. We
had told him the map was incomplete, but when we asked him about what he was seeing, he
pointed to a spot on the map and somewhat reluctantly stated that he thought that there was
a theatre at that location. Before we could remind him that these were purposely incomplete
draft maps, he continued: he was
sure
he had been to a movie at that location, but he
doubted himself because the theatre was not on the map. He must have been mistaken, he
thought.
This all-too-common response to a map has haunted responsible cartographers - and
delighted less scrupulous ones - for many years. We know that many incorrect conclusions
and detrimental decisions are made from an unquestioning and uncritical use of maps,
resulting in mistakes that range from the innocuous, such as missing a turn because the
GPS map did not show the road, to the catastrophic, such as bombing a national embassy
because the map used was not current (Reuters, 2006).
GIScience researchers, educators and students know that there is a multitude of reasons
that our representations of geographic reality are incomplete and uncertain. Measurements
cannot be taken at every location and can only obtain a certain level of accuracy. Observations
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