A Framework and Methods for Characterizing Uncertainty in Geologic Maps

Geologic maps are products of complex analyses and interpretations, and as such, contain a certain amount of uncertainty. Unfortunately, it is difficult to estimate the uncertainty within a geologic map. Much of this difficulty is due to the lack of a clear framework for describing the sources of uncertainty within the map and poor awareness, within the mapping community, of methods capable of estimating these sources of uncertainty. Mann (1993) provides a discussion of uncertainty in geology and a framework for identifying the sources of uncertainty. His discussion is not limited to maps, but focuses more on data. Bardossy and Fodor (2001) use Mann’s (1993) framework and extend his ideas by proposing four groups of mathematical methods that can be applied to characterize uncertainty in geology. Their discussion provides some innovative suggestions of methods for estimating uncertainty. As with Mann’s (1993) treatment, they focus most of their discussion on data issues and do not provide any recommendations for conducting a comprehensive evaluation of uncertainty within geologic maps. I will present a framework for characterizing the sources of uncertainty in geologic maps which builds significantly on the insights provided by Mann (1993). I will extend Bardossy and Fodor’s (2001) discussion by presenting a larger suite of practical methods for characterizing the uncertainty in geologic maps due to these different sources. Finally, I will briefly discuss concerns for conducting a more comprehensive, integrated evaluation of uncertainty in geologic maps and for interpreting and applying the results from such a comprehensive uncertainty analysis.