Why are soil mapping units important?
Map scale determines the appropriate mapping unit 1. For instance, there are 12 soil orders 5 in the US Soil Taxomony and 15,000 recognized soil series 3. One can imagine a map of the US showing the distribution of 12 types of soils but how could you display 15,000 different soils? The soils of a single county may belong to only one or two soil orders but may include 20 soil series. A county soil map with only two soil order map units would convey much useful information but one displaying 10-20 soil series or soil associations would be far more informative.
