Significance and application of the multi-hierarchical landsystem in soil mapping

A methodological framework to formalise the landscape knowledge of the soil surveyor is presented. It requires structuring of terrain objects in a nested hierarchy, followed by inference and formalisation of knowledge rules. We demonstrate how these rules can be applied in a GIS environment for learning and communicating knowledge. Object subdivision is based on the technique of hierarchical subdivision derived from surveyor experience. Formalisation of contextual knowledge requires (1) description of the semantics of object levels in relation to scale, (2) definition of objects and attributes and their relation to higher and lower level objects, and (3) the knowledge inferred from the objects and its inclusion in the database. The Alora case study (South Spain) illustrates the value of the different object levels of the hierarchy for obtaining information on both soils and land evaluation. Often more than one context (object hierarchy) has to be considered to predict this information. We argue that a GIS database requires proper description of the different kinds of formal relationships that exist between objects and object classes, and between elementary and composite objects. We also show that the different scale levels of the multiple hierarchy play an essential role in conveying knowledge for an interdisciplinary application (land evaluation, land use, erosion, and hydrology). (C) 2001 Elsevier Science B.V. All rights reserved.