The Expector Method provides an excellent basis for modelling soil and other environmental classes or properties using a combination of expert knowledge and empirical data. The ideas are based on probability theory, and hence can be given a rigorous mathematical underpinning. Nevertheless, concerns have arisen regarding the published algebra used in deriving the equations underlying the model. We present corrections to key equations, improved notation to encourage future use of this methodology, and a simplification of the map purity extension to the formula that allows different weights to be applied to the evidence layers. We illustrate the methodology with an example of mapping soil parent materials.
['Timothy S. Farewell', 'Daniel Farewell']
Knowledge-based soil attribute mapping in GIS: corrections and extensions to the expector method