The soil survey map does not describe soil point by point: it divides the territory into polygons and describes each one. That polygon is the map unit, and it is the finest grain that exists. Within a unit, all data is the same.
A unit is rarely a single soil. It is usually an association or consociation of several series, each with its percentage. A name like “enthic Haplustoles” describes the dominant soil, not the only one.
| Unit type | What does it mean |
|---|---|
| Consociation | One series clearly dominates; the rest are minor inclusions |
| Association | Two or more series coexist in comparable proportions |
| Complex | The series intermingle so finely that they cannot be separated when mapping |
| Undifferentiated group | Different series grouped because their use is equivalent |
The report of a property lists the units that cover it with the percentage of surface of each one, and discards those that contribute less than 15%: a patch of three hectares of another texture does not define a property of two hundred.
The unit and series names are official INTA nomenclature and are not translated. If they were translated, the data would no longer be able to be compared against the original soil survey map.