Profile height is considered positive above the mean line and negative below the mean line. A profile peak is a region of the profile that lies above the mean line and intersects the mean line at each end. In the figure below, each shaded region is a peak. The height of a peak is defined to be the point of maximum height within the region. Profile peaks are regions above the mean line.
Local peaks are regions between two local minima.
A profile valley analogous to a profile peak is a region of the profile that lies below the mean line and intersects it at each end. The depth of a valley is the depth of the lowest point within the valley. Sometimes it is convenient to speak of one profile peak together with one adjacent profile valley as a profile irregularity. Profile Valleys extend below the mean line. A local peak is a region of a profile between two successive local minima in the profile.