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Mean profile element spacing Rsm is the arithmetic mean of the pro­file element spacings Xsi of the rough­ness profile. A profile ele­ment is a hill fol­lowed by a dale or a dale followed by a hill.

The evaluation is thus performed in two directions. Generally, the thresh­olds to detect a profile element are 10% Rp and 10% Rv.


Root mean square gradient Rdq is the root mean square value of the local profile leads of the rough­ness profile.

The local profile leads are calculated using a smoothing func­tion to suppress any noise in­fluence.