# Hyperlink 5. Sample Support

Defining the soil volume of interest requires knowing the spatial dimensions of a DU, including its area, depth, shape, and orientation in space. These spatial characteristics are collectively called the “support.” Since these characteristics apply to the target for decision making, it is called a “decision support.” The same spatial characteristics apply to samples taken from the decision support and are referred to as the “sample support.” “Sample support” is the more general term, although the term “subsample support” might also be used as appropriate.

A criterion of sample representativeness is that the sample support must mirror the decision support. For example, if the depth of the DU is 12 inches, then the sample support depth should be 12 inches. If the area of the decision support is 5000 ft2, then the samples should come from that same 5000 ft2 area. The decision support is the basis for identifying the dimensions of DUs in ISM designs. The area and shape of the DU can be blanketed with increments so that the sample mirrors the same dimensions of the DU. When a single sample is taken from the center of an area with discrete sampling, there is no natural sense of where the boundaries of the DU are, and there is no reason to assume that the sample is physically representative of some defined area. With ISM, the incremental sample is designed to closely match the DU.