Various components of surface texture are identified, namely form, waviness and roughness. Separation of these components is done by digital filtering. Several problems exist during analysis of two-process surfaces. Therefore the Gaussian robust profile filtering technique was established and has been studied here. The computer generated 2D profiles and 3D surface topographies having triangular scratches as well as measured stratified surfaces were subjected to filtration. However even robust filter applications cause distortion of profiles having valleys wider than 100 μm. In order to minimize the distortion associated with wide and deep valleys, the robust filter should be modified. A special procedure was elaborated for minimizing distortion of roughness profiles caused by filtration. Application of this method to analyses of several profiles was presented. The difference between 1-D and 2-D filtering of surface topography using the same kind of filter was discussed. As a result we found that modification of a 2-D surface topography filter was not necessary.

In this paper distortion of surface topography measurement results by improper selection of the reference plane is taken into consideration. The following types of surfaces from cylindrical elements were analyzed: cylinder liners after plateau honing, cylinder liners with additionally burnished oil pockets and turned piston skirts. Surface topographies of these elements after a low wear process were also studied. In order to obtain areal surface topography parameters, the form was eliminated using cylinders and polynomials of the following degrees: 2, 3, 4, 6, 8, 10 and 12. Parameters of surfaces after form removal were compared. After analysis of results the reference elements for each kind of surface were recommended. A special procedure was proposed in order to select the degree of a polynomial. This method is based on surface topography changes with increase of polynomial degree. The effect of improper form elimination on measuring uncertainty was studied.