A surface measurement method includes inspecting a plurality of samples of a first irregular workpiece surface in two dimensions, determining, based on the inspections of the samples, a total number of surface peaks on each of the plurality of samples, and deriving a control limit from a statistical variation of the total number of surface peaks on each of the samples. The control limit specifies an out-of-tolerance condition for the total number of surface peaks on a second irregular workpiece surface. The method further includes inspecting a portion of the second irregular workpiece surface in two dimensions, determining, based on the inspection of the portion of the second irregular workpiece surface, a total number of surface peaks on the portion, and comparing the total number of surface peaks on the portion to the control limit to determine whether the second irregular workpiece surface is in the out-of-tolerance condition.