ISO 16610-61:2015

Overview

ISO 16610-61:2015 is an ISO GPS (Geometrical Product Specification) standard that defines linear areal Gaussian filters for surface filtration. It specifies metrological characteristics and procedures for the rotationally symmetric filtration of nominal planar surfaces and the filtration of nominal cylindrical surfaces. The standard focuses on how to separate a surface into long-wave (form/shape) and short-wave (texture/roughness) components using Gaussian areal filters.

Key topics and technical requirements

• Filter type: Linear areal Gaussian filters (rotationally symmetric) for planar and cylindrical surfaces.
• Weighting function: Defined by a rotational Gaussian function with a cut-off wavelength (λc) and a constant α (α ≈ 0.4697) that gives 50% transmission at λc.
• Transmission characteristics: Long-wave and short-wave transmission functions are derived by Fourier transformation of the weighting function; the cut-off wavelength (nesting index) is the wavelength transmitting 50% amplitude.
• Separable filters: The areal Gaussian weighting function is separable into orthogonal profile Gaussian functions, enabling two-step profile filtering (convolution separability) to improve computational efficiency.
• Cylindrical filtration: For nominal cylinders, the circumferential (T) direction uses a wrapped (closed-profile) Gaussian weighting function; concepts such as undulations per revolution (UPR) and undulation cut-off are used.
• Practical parameters: Truncation index L (filter window) must be chosen appropriately; too small L can introduce unacceptable systematic error.
• Normative references: Linked to ISO 16610‑1, -20, -21, -60 and ISO/IEC guides for metrology and uncertainty.

Applications and who uses it

ISO 16610-61 is relevant to anyone performing surface texture and form analysis where consistent, traceable filtration is required:

• Quality/control engineers and metrologists validating surface texture and roughness.
• Manufacturers and suppliers of coordinate-measuring machines (CMMs), profilometers and areal surface scanners.
• Inspection and calibration laboratories implementing GPS-compliant procedures.
• Process engineers and R&D teams optimizing machining, polishing or coating processes by separating form and texture components.
• Software developers for metrology and CAD/CAM tools implementing areal filtering algorithms.

Practical uses include surface roughness evaluation, separation of form and waviness from texture, roundness and circumferential profile analysis (using UPR), and implementation of reliable areal-filtering algorithms in measurement software.

Related standards

• ISO 16610-1: Overview and basic terminology (GPS filtration)
• ISO 16610-20 / -21: Linear profile filters and Gaussian profile filters
• ISO 16610-60: Linear areal filters - Basic concepts
• ISO/IEC Guide 99 and Guide 98-3: Metrology vocabulary and uncertainty

Keywords: ISO 16610-61, Gaussian filters, linear areal filters, filtration, surface texture, cut-off wavelength, nesting index, GPS, areal filtering, cylindrical filtration.