SOIL SURVEY

the maps by local geographic names such as Ogden (OG) . Some of the soilscap egroups were then further subdivided into map units on the basis of texture (of th efine earth fraction), coarse fragment contents and drainage . These subdivisions aredenoted by a number after the name (e .g . OG1 and OG2) . Some of the soilscapegroups were not further subdivided resulting in only one map unit within that grou pconcept . When, within a given soilscape group, changes in textural class, coars efragments or drainage occurred in areas too small to separate cartographically, newmap units were not established . Rather, the map unit description indicated the kin dof variation occurring and a discussion of where the variants were located on th elandscape . Also, new map units were not established when the areal extent of th eproposed map unit was insignificant relative to the areas of the other map units ,and the nature of the variation did not result in a highly contrasting concept fro mthe most similar existing map unit . Again the variability and its relation to th elandscape was described in the map unit description .The map units as delineated on the aerial photographs were continuousl yupdated as the map unit concepts changed, so that when the map unit concept swere finalized, the map unit boundaries as delineated on the aerial photograph swere representative of those final map unit concepts . Representative pedons (soi lprofiles) were described and sampled to characterize the map units . Thus, each ma punit concept is a composite of the information obtained from the aerial photographs ,the field analyses and the chemical and physical analyses conducted in the laboratory .The location of each pedon chosen to represent the soi Iscape map units is shown o nFigure 16 .