Overview
EN ISO 16610-62:2023 - "Geometrical product specifications (GPS) - Filtration - Part 62: Linear areal filters: Spline filters" - defines the characteristics and behaviour of linear areal spline filters used in surface metrology. The standard specifies a low-pass areal filter based on cubic splines that preserves global shape (global shape retainment) while separating long-wave (form/waviness) and short-wave (roughness) components on surface topography maps.
Key topics and technical requirements
- Filter type and scope
- Defines the linear areal spline filter as the areal extension of the linear profile spline filter (ISO 16610-22).
- Covers both linear planar filters (open surfaces) and linear cylindrical filters (surfaces with periodic continuation).
- Mathematical formulation
- Presents a low-pass filter formula for cubic spline filters on uniformly sampled grids, using transformation matrices (Ax, Ay) applied to the input height map.
- Specifies matrices for discretized differentiation (P, Q) and the unity matrix E used in the filter matrices.
- Key parameters
- Regularization parameter (α, μ) - relates spline smoothness to the cut-off wavelength (λc); determines degree of smoothing.
- Tension parameter (β) - influences the slope of the transfer function (transmission characteristics).
- Guidance for computing αx, αy for lateral axes and modifications for distorted sampling grids.
- Transmission characteristics and filter designation
- Defines the cut-off wavelength convention (50% amplitude transmission) and identifies how the spline filter is designated (filter type plus cut-off).
- Normative structure and relationships
- Includes informative annexes linking the spline filter to the filtration matrix model and the GPS matrix model.
Applications and users
EN ISO 16610-62:2023 is intended for professionals involved in surface texture measurement, analysis and specification:
- Metrology laboratories and calibration facilities performing areal surface measurements.
- Quality and process engineers specifying surface requirements (roughness, waviness) for components.
- Instrument and software developers implementing areal filtering algorithms for profilometers, confocal microscopes and optical profilers.
- Manufacturing sectors where surface topography affects function: bearings, seals, optics, medical devices, and precision machined parts.
Practical uses include extraction of waviness from measured topography maps, setting cut-off wavelengths for areal analyses, and ensuring consistent filtering for GPS-compliant surface specifications.
Related standards
Keywords: EN ISO 16610-62:2023, spline filters, linear areal filters, filtration, GPS, cut-off wavelength, regularization parameter, tension parameter, surface metrology, topography maps.