Pilot points have been used in geophysics and hydrogeology for at least 30 years as a means to bridge the gap between estimating a parameter value in every cell of a model and subdividing models into a small number of homogeneous zones. Pilot points serve
Doherty, John E.,Fienen, Michael N. mnfienen@usgs.gov,Hunt, Randall J. rjhunt@usgs.gov. Approaches to highly parameterized inversion: Pilot-point theory, guidelines, and research directions. 2011-01-01.