Where map legends and map unit definitions reflect the mental models used by soil surveyors to map soils in the past, the association between soil map units and other environmental spatial data can be re-modelled to infer formal survey rules. These rules then can be used to guide subsequent re-interpretations of spatial information for the same area or for another area judged to be similar. Classification trees and Bayesian statistical modelling were used to extract soil mapping rules from an existing map using the Toowoomba area in south-eastern Queensland, Australia, as a case study. In the Toowoomba map area, regional soil-landscape rules could be extracted by combining geology and DEM-derived attributes. The two approaches achieved comparable success.