The committee was tasked to determine the best instrumentation and procedures for measuring BFD (see Box S-1). To do this, it reviewed technical specifications, viewed demonstrations of the operation and use of current and prospective systems, and evaluated factors such as human handling variability, process transparency, and software variability judgment. The committee found that given the current clay variation, a measurement precision (standard deviation) of mm is sufficient; instruments featuring greater precision add little practical value to the testing process. Future improvements in the inherent variability of the backing material will require instruments that are correspondingly more precise. It is important that quantified data from actual tests be obtained.
