Land classification is essential for geographers, planners, and, increasingly, for environmental scientists (Owen et al. (2006) Landsc. & Urb. Plan. 78, 4). There is ‘no single correct way to describe reality and solve practical questions’ regarding the classification of land cover, and all classifications are subjective. Thus, the quality of the classification depends on the skill of the interpreter (Lofvenhaft et al. (2002) Landsc. & Urb. Plan. 58, 2–4). The Food and Agriculture Organization of the United Nations Land Cover Classification System uses an initial dichotomous phase, where the user derives the main land cover type, and a subsequent modular-hierarchical phase, where a land cover class is defined by determining one classifier at a time.

http://www.fao.org/docrep/003/x0596e/x0596e00.htm The FAO Land Cover Classification System.