The DU should not be confused with the coefficient of uniformity (CU) which is often preferred for describing the performance of overhead pressurized systems.
The most common measure of DU is the low quarter DU expressed as DUlq, which is a measure of the average of the lowest quarter of samples, divided by the average of all samples expressed as percentage.
The lower the DU, the less uniform the distribution at the plane of data collection and the more water that may be needed to meet the minimum requirement.
Many factors may affect water distribution or redistribution between catchment plane and root zone; slope, plant canopy, thatch, mulch, infiltration rate, etc..
Soil type and root horizon may nullify the need for high DUlq sprinklers.