Driven by the intended mapping scale and the concept of a “minimum mapping unit”, polygon based land resource mapping techniques involve the filtering out of smaller soil bodies and landscape features deemed to small to be represented on a printed map at the desired scale which leads to generalisation of the landscape. The result is the production of maps that represent the distribution of a prescribed set of dominant soil classes but do not represent the actual spatial distribution of soils (Zhu et al., 2001). The natural landscape comprises heterogeneous patches bounded by transition zones of variable width that represent

1 INTRODUCTION

Integrated land resource surveys, involving the concurrent collection of soil, landform and vegetation field data, have been conducted in the Northern Territory since the 1960s and provide the foundation for our current knowledge and understanding of the soil-landscape and landscape processes. These surveys have been produced at a range of scales; fine scale land unit mapping (1:25 000 to 1:100 000 scale) and reconnaissance scale land system mapping (up to 1:1 000 000) that together cover most of the Northern Territory. Land units are areas that comprise reasonably homogenous landform, soils and vegetation though each unit can also include minor areas of other soil, vegetation and/or landform considered too small to be mapped separately (Hill et al., 2002). Land systems represent groupings of recurring patterns of land units.