The Environmental Zones are aggregations of ITE Land Classes; these classes are derived from repeatable multivariate analysis of environmental data collected for each 1 km square in the country. Thus the classes, and hence the zones, are determined by combinations of environmental characteristics, not by just one or two. This means that the naming of classes (and zones) is not straightforward and cannot be achieved by reference to single parameters such as altitude. The approach taken with the ITE Land Classes is to give each a numeric identifier, rather than a text name, and to supplement these Land Class numbers with a brief description of the class.