Academic journal article Cartography and Geographic Information Science

Testing the Effects of Thematic Uncertainty on Spatial Decision-Making

Academic journal article Cartography and Geographic Information Science

Testing the Effects of Thematic Uncertainty on Spatial Decision-Making

Article excerpt


With the growing use of Geographic Information Systems (GIS), the applications of spatial information have become more sophisticated and diverse. Decisions are increasingly being made on the basis of information that is derived from GIS, and the users of these systems may have little or no knowledge of the processes underlying the output products. Although the systems may be computationally precise, the outputs of a GIS can only be as accurate as the data inputs. In recent years, it has been recognized that both the quality of the input data and the resultant effect on the information outputs need to be fully understood if the decisions being made are to be considered robust and informed. However, to date there has been relatively little research conducted into how the inclusion of uncertainty information and the mode of its representation may influence decision-making.

We now accept that errors and uncertainties are inherent in spatial data, and the need for metadata concerning the lineage and accuracy of a dataset is widely accepted. Data transfer standards that include provision for metadata description, such as the U.S. Spatial Data Transfer Standard, have been established in many countries and more recently the International Organization for Standardization has finalized several standards relating to spatial data quality. However, while most spatial data producers now provide metadata with their datasets, researchers such as Hunter (2001) have cited several examples of poor metadata reportage along each of the identified quality elements. He has also emphasized the need for greater detail in metadata reporting (Hunter and Goodchild 1997) and the provision for data quality information at local feature class and feature levels, as well as at the global dataset level (Qiu and Hunter 2002).

Furthermore, while the provision of metadata embedded within spatial datasets is becoming more widespread, their ability to communicate uncertainty is still considered quite limited. Frank (1998) contends that metadata are written from the perspective of the data provider and, as a result, do not necessarily meet user requirements. Indeed, Keuper (2004) found that few consumers of spatial information, including those with substantial experience, give much consideration to the information provided in metadata reports. Thus there is growing recognition, at least within the academic community, that: (1) the functionality of GIS needs to be enhanced to include ways of representing uncertainty; and (2) such representations need to communicate the uncertainty in a manner that is unambiguous, fully informative, and better able to facilitate decision-making.

For that functionality to be most effective we need to know how users of spatial information react to the presence of additional uncertainty information when they are required to make decisions. This calls for cognitive testing in a decision-making environment, and we have sought evidence and indicators from the psychological literature to refine our observations. In this paper we confine our testing to the effects of introducing thematic uncertainty information to spatial decision-making, however, a companion paper has been written that addresses the issue with respect to positional uncertainty.

We begin with a background to our study in terms of the reported research in the spatial information and psychological literature, followed by sections that describe the case study and our method, respectively. We then explain the participating groups used and the way the experiment was conducted, followed by sections presenting the experimental results and discussion.


In the early 1990s, the National Center for Geographic Information and Analysis (NCGIA) established a research initiative focusing on the issue of visualization of spatial data quality (Beard et al. 1991). Research challenges were identified in the areas of communicating data quality to users, error propagation through GIS operations, and the application of data quality information to decision-making--in addition to metadata reporting. …

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