BS EN ISO 16610-29:2020 pdf free.Geometrical product specifications (GPS)一Filtration.
Wavelet analysis consists of decomposing a profile into a linear combination of wavelets ga,b(x), all generated from a single mother wavelet. This is similar to Fourier analysis, which decomposes a profile into a linear combination of sinewaves, but unlike Fourier analysis, wavelets are finite in both spatial and frequency domain. Therefore, they can identify the location as well as the scale of a feature in a profile. As a result, they can decompose profiles where the small-scale structure in one portion of the profile is unrelated to the structure in a different portion, such as localized changes (i.e. scratches, defects or other irregularities). Wavelets are also ideally suited for non-stationary profiles. Basically, wavelets decompose a profile into building blocks of constant shape, but of different scales.A fast implementation of the wavelet decomposition and reconstruction has been employed using a lifting scheme with three stages: splitting, prediction and updating, originally introduced by Sweldens, in which the Neville polynomials are employed to implement the prediction stage by interpolating between sampling positions[6,7]. The cubic prediction wavelets in Annex A using Sweldens’ lifting schemel6] has been validated as an efficient tool for fast and in-place wavelet transform for geometrical products applications, for example surface metrology[2]. Spline wavelets are based on the spline function. In this document a cubic b-spline function is used, which has a compact support. The particular cubic spline wavelets used are the biorthogonal wavelets CDF 9/7 with four vanishing moments, detailed in Annex B. This was original introduced by Cohen et al.[8] and has been used in geometrical products applications, for example multiscale analysis. The cubic spline wavelet transform can be implemented using both the Fourier method and the lifting scheme (however, it is a five-stage process) with relevant precision. These cases are considered in order to guarantee boundary “naturalness”, without including any artefacts (all filtering factors are indicated in Table A.1). The result of this is that running-in and running-out lengths of normal filtering techniques are not needed. BS EN ISO 16610-29 pdf download.