A soil survey procedure using the knowledge of soil pattern established on a previously mapped reference area

Abstract

Mapping rules based on the knowledge of regional soil patterns — soil pattern rules — can be acquired from a previous soil survey of a small but representative sample area called the reference area. They can then be used in new soil surveys carried out on wider areas; this allows both to select the observation points and to predict which soil unit occurs at non-observed points. A quantified formulation of these rules is proposed to use them within an automated soil survey procedure. The soil pattern rules of a reference area are formulated through rules which give probabilities of soil unit presence. These probabilities are then combined to give soil predictions outside the reference area from a set of observation points. The observation points are successively chosen by the soil survey procedure according to a pre-defined strategy which takes into account the estimated uncertainty of the earlier predictions. The technique was tested on the Middle Valley of the Herault river (France). Comparisons between actual and simulated soil maps show good results both in terms of quality and optimization of the number of observation points. Although further work is needed to achieve a fully operational tool, the soil survey procedure tested looks promising for regions with identifiable and repeating soil patterns.