Cartographica (2004) 39(2): 15-28.

Protection of Geoprivacy and Accuracy of Spatial
Information: How Effective Are Geographical Masks?

Mei-Po Kwan

Abstract: Spatial analysis and mapping of georeferenced individual-level data can help identify important geographical patterns or lead to significant knowledge for dealing with specific social issues in a particular area. However, given the need to protect personal privacy when using geospatial data, the possibility for undertaking geographical analysis on certain types of individual-level data is becoming increasingly circumscribed. This paper addresses the need to protect geoprivacy while making individual-level georeferenced data available in such a way that analytical results are not significantly affected. Using a data set of lung cancer deaths in Franklin County, Ohio in 1999, the effectiveness of three geographical masks with different perturbation radii (r) is examined. The findings reveal a rather consistent tradeoff between data confidentiality and accuracy of analytical results. There seems to be a threshold r value at which the results of analyses on masked data become substantially different from the original results. An r that produces an area about the average size of the census block groups of the study area achieves a desirable optimum trade-off between privacy protection and accuracy of results. The study shows that implementing appropriate geographical masks may help data managers or researchers establish the desirable level of trade-off between privacy protection and accuracy of geographic information in a particular context.

Key Words: geoprivacy, GIS, privacy, geographical mask, disaggregate data, lung cancer deaths, accuracy

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