Surface topography assessments with valley exploration are of great importance. Two-process surfaces are often proposed for many combustion engines. One of the errors committed in surface topography measurements and analysis are those that occur during data processing. In this paper, improper areal form removal was taken into consideration for plateau-honed cylindrical surfaces with additionally burnished oil pockets. Usually, the reference plane is established by application of: fitting algorithms (eg cylindrical shape), polynomials, filters and other procedures. In many cases, the influence of the reference plane was not fully recognized during valley depth consideration. Moreover, the influence of areal form removal with edge-to-dimple and valley-to-dimple distances was not precisely defined. In this research, commonly used algorithms for form separation in surface topography analysis were proposed for the applications being considered. The digital filter bandwidth was also specified for valley depth analysis. The distortion of edge-located oil pockets was specified. It was assumed that application of robust techniques does not necessarily provide the desired results.