Many test charts popularly used for color output characterisation purposes, are based on a regular orthogonal sampling of device space. Mathematically such a rectangular sampling is not the most efficient way of exploring a multidimensional space, so an alternative based on a simplex sampling of device space has potential for improving the efficiency of device profiling, requiring fewer test point for a given profile accuracy, or returning a higher profile accuracy for a given number of test points.
Graeme W. Gill, "Improved output device characterisation test charts" in Proc. IS&T 12th Color and Imaging Conf., 2004, pp 200 - 202, https://doi.org/10.2352/CIC.2004.12.1.art00036