A.2.1 The main differentiator between the ISO 4287 and ISO25178 is how the acquired data set is processed to maximizethe accuracy of the calculated roughness values. The oldstandard used terms like λs and λc to account for the stylustip size and total evaluation length, which are specific towardscontact profilers. The newest standard uses filters to accountfor similar features of noncontact 3-D profilers: the objectivelens used for analysis and total XYZ coverage area. Listed below is additional detail to describe how the S-filter,F-operation and L-filter are defined