FprEN ISO 25178-71

Geometrical product specifications (GPS) - Surface texture: Areal - Part 71: Surface data file (SDF) file format (ISO/FDIS 25178‑71:2026)

ISO 25178-71:2017 defines Type S1 and Type S2 software measurement standards (etalons) for verifying the software of measuring instruments. It also defines the file format of Type S1 software measurement standards for the calibration of instruments for the measurement of surface texture by the areal method as defined in the areal surface texture chain of standards, chain link G.
NOTE       Throughout ISO 25178-71:2017, the term "softgauge" is used as a substitute for "software measurement standard Type S1".

Geometrische Produktspezifikation (GPS) - Oberflächenbeschaffenheit: Flächenhaft - Teil 71: Software-Normale (ISO/FDIS 25178‑71:2026)

Dieses Dokument legt Software-Normale vom Typ S1, Referenzdaten, und Software-Normale vom Typ S2, Referenzsoftware, zur Verifikation der Software von Messinstrumenten fest. Es legt außerdem das SDF-Dateiformat der Software-Normale vom Typ S1 zur Kalibrierung von Messgeräten zur profil- und flächenhaften Messung der Oberflächenbeschaffenheit fest, wie sie für die Kettenglieder F und G der Normenkette über die Oberflächenbeschaffenheit festgelegt sind.
Das SDF-Dateiformat ist anwendbar auf profil- und flächenhafte Topographie-Messdaten, die mithilfe eines orthogonalen Gitters (siehe ISO 14406:2010, 5.2) und äquidistanten Abtastintervallen extrahiert wurden, unabhängig vom Messprinzip.
ANMERKUNG   In diesem Dokument werden durchgehend die Begriffe „Referenzdaten“ und „Referenz-Software“ als Ersatz für den Begriff „Software-Normal vom Typ S1 bzw. Typ S2“ verwendet. In der Praxis werden „Referenzdaten“ bisweilen als „Software-Normal“ oder „Software-Lehre“ bezeichnet.

Spécification géométrique des produits (GPS) - État de surface: Surfacique - Partie 71: Étalons logiciels (ISO/FDIS 25178‑71:2026)

L'ISO 25178-71:2017 définit les étalons logiciels de Types S1 et S2 qui permettent de vérifier les logiciels des instruments de mesure. Il définit également le format de fichier des étalons logiciels de Type S1 utilisés pour l'étalonnage des instruments de mesure d'état de surface, conformément à la méthode surfacique telle que définie dans le maillon G de la chaîne de normes sur l'état de surface surfacique.
NOTE       Dans l'ISO 25178-71:2017, le terme «étalon logiciel» désigne un «étalon logiciel de Type S1».

Specifikacija geometrijskih veličin izdelka (GPS) - Tekstura površine: Ravna - 71. del: Standardi za merilno programsko opremo (ISO/FDIS 25178‑71:2026)

General Information

• Status: Not Published
• Publication Date: 12-Oct-2026
• ICS: 17.040.20 - Properties of surfaces
• ICS: 17.040.40 - Geometrical Product Specification (GPS)
• Technical Committee: CEN/TC 290 - Dimensional and geometrical product specification and verification
• Current Stage: 5020 - Submission to Vote - Formal Approval
• Start Date: 21-May-2026
• Completion Date: 21-May-2026
• Ref Project: kSIST FprEN ISO 25178-71:2026 - Geometrical product specifications (GPS) - Surface texture: Areal - Part 71: Software measurement standards (ISO/FDIS 25178‑71:2026)

Relations

• Consolidated By: ISO/FDIS 25178-71 - Geometrical product specifications (GPS) — Surface texture: Areal — Part 71: Surface data file (SDF) file format
• Effective Date: 12-Feb-2026
• Revises: EN ISO 25178-71:2017 - Geometrical product specifications (GPS) - Surface texture: Areal - Part 71: Software measurement standards (ISO 25178-1:2017)
• Effective Date: 17-Jan-2024

Overview

FprEN ISO 25178-71 defines the requirements for software measurement standards, specifically for verifying the software used in measuring instruments that assess areal surface texture. Developed by CEN, this standard details both Type S1 (softgauge) and Type S2 reference software standards, and provides a standardized file format - the Surface Data File (SDF) - for managing reference data for calibration purposes. By standardizing the SDF format, FprEN ISO 25178-71 facilitates the reliable testing, verification, and calibration of measuring instrument software in line with the areal method defined in the ISO GPS system.

Key Topics

• Software Measurement Standards: The standard introduces two core types:
  • Type S1 (Softgauge): Digital files containing measured or mathematically generated surface data, mainly used for verifying the computation algorithms in measurement software.
  • Type S2 (Reference Software): Traceable software tools that serve as benchmarks for evaluating metrological computations within measuring instruments.
• SDF File Format: Specifies a standardized layout for recording surface topography data:
  • Header: Captures essential metadata about the measurement, such as instrument manufacturer, creation/modification dates, grid sizes, scaling factors, data type, and version information.
  • Data Area: Contains the matrix of height data from surface measurements, facilitating unambiguous data interchange and algorithm validation.
  • Trailer: Allows storage of variable-length metadata, such as operator input, measurement conditions, and any data processing steps.
• Data Integrity & Compatibility: The SDF format includes support for versioning, clear treatment of non-measured or spurious points, and guidelines for ASCII and binary encodings, improving robustness and compatibility across software systems.
• Calibration & Certification: Mandates that every software measurement standard be accompanied by a calibration certificate, detailing values, uncertainties, calibration methods, and traceability.

Applications

The ISO 25178-71 standard is crucial for industries and laboratories where surface texture measurement, quality control, and metrological traceability are required. Key areas of application include:

• Instrument Calibration: Ensures that software managing areal surface measurements is functioning correctly, providing reliable, traceable results.
• Software Development & Testing: Surface measurement software developers use S1 and S2 standards to validate algorithms for surface characterization and data processing.
• Quality Assurance: Manufacturers and laboratories leverage conforming software and data formats to maintain compliance with international product specification requirements.
• Data Exchange & Interoperability: Standardizing the SDF file format enables seamless data communication between different hardware and software platforms, essential for collaborative projects, regulatory submissions, or multi-vendor environments.

Related Standards

• ISO 25178 Series: This is part of the broader ISO 25178 family focusing on areal surface texture.
• ISO 14638: Outlines the GPS matrix model, which the 25178-71 standard references.
• ISO 14406: Defines requirements for the orthogonal grid and sampling intervals for areal measurement.
• ISO 8015 and ISO 14253-1: Provide general GPS rules for product specifications and default decision-making rules.
• ISO/IEC Guide 99: Establishes the international vocabulary of metrology, referenced for terminology consistency.

Practical Value

By implementing FprEN ISO 25178-71, industries ensure reliable verification and calibration of surface metrology software, improve cross-compatibility, reduce risks of measurement errors, and streamline product quality management. Standardization of measurement data files cultivates trust and transparency throughout the manufacturing and certification processes, supporting global trade and regulatory compliance.

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN ISO 25178-71:2025
01-oktober-2025
Specifikacija geometrijskih veličin izdelka (GPS) - Tekstura površine: Ravna - 71.
del: Standardi za merilno programsko opremo (ISO/DIS 25178-71:2025)
Geometrical product specifications (GPS) - Surface texture: Areal - Part 71: Software
measurement standards (ISO/DIS 25178-71:2025)
Geometrische Produktspezifikation (GPS) - Oberflächenbeschaffenheit: Flächenhaft –
Teil 71: Software-Normale (ISO/DIS 25178-71:2025)
Spécification géométrique des produits (GPS) - État de surface: Surfacique - Partie 71:
Étalons logiciels (ISO/DIS 25178-71:2025)
Ta slovenski standard je istoveten z: prEN ISO 25178-71
ICS:
17.040.20 Lastnosti površin Properties of surfaces
17.040.40 Specifikacija geometrijskih Geometrical Product
veličin izdelka (GPS) Specification (GPS)
35.080 Programska oprema Software
oSIST prEN ISO 25178-71:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 25178-71:2025
oSIST prEN ISO 25178-71:2025
DRAFT
International
Standard
ISO/DIS 25178-71
ISO/TC 213
Geometrical product specifications
Secretariat: BSI
(GPS) — Surface texture: Areal —
Voting begins on:
Part 71: 2025-06-02
Software measurement standards
Voting terminates on:
2025-08-25
Spécification géométrique des produits (GPS) — État de surface:
Surfacique —
Partie 71: Étalons logiciels
ICS: 17.040.20; 17.040.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 25178-71:2025(en)
oSIST prEN ISO 25178-71:2025
DRAFT
ISO/DIS 25178-71:2025(en)
International
Standard
ISO/DIS 25178-71
ISO/TC 213
Geometrical product specifications
Secretariat: BSI
(GPS) — Surface texture: Areal —
Voting begins on:
Part 71:
Software measurement standards
Voting terminates on:
Spécification géométrique des produits (GPS) — État de surface:
Surfacique —
Partie 71: Étalons logiciels
ICS: 17.040.20; 17.040.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 25178-71:2025(en)
ii
oSIST prEN ISO 25178-71:2025
ISO/DIS 25178-71:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Type S software measurement standards . 4
4.1 General .4
4.2 Type S1, reference data .4
4.3 Type S2, reference software .4
5 File format for Type S1 reference data . 4
5.1 General .4
5.2 Record 1 — Header .5
5.2.1 General .5
5.2.2 Version number .5
5.2.3 Measurement instrument manufacturer's identifier .5
5.2.4 Original creation date and time .5
5.2.5 Last modification date and time.5
5.2.6 Number of columns in the data matrix, N .5
5.2.7 Number of rows in the data matrix, M .5
5.2.8 X-scale factor .5
5.2.9 Y-scale factor .5
5.2.10 Z-scale factor . .6
5.2.11 Z-resolution .6
5.2.12 Compression type .6
5.2.13 Data type .6
5.2.14 Checksum type . .6
5.2.15 Header description .6
5.3 Record 2 — Data area .7
5.3.1 General .7
5.3.2 Handling of non-measured or spurious points . .8
5.4 Record 3 — Trailer .8
6 Software measurement standard certificate . 9
Annex A (normative) ASCII and binary representation of the SDF format .10
Annex B (informative) Relation to the GPS matrix model .12
Bibliography .13

iii
oSIST prEN ISO 25178-71:2025
ISO/DIS 25178-71:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product
specifications and verification.
This third edition cancels and replaces the second edition (ISO 25178-71:2017), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the version number 2.0 has been added, which incorporates a number of new functionalities;
— in version number 2.0, the number of columns and the number of rows of the data matrix is represented
as a 4-byte unsigned integer instead of a 2-byte unsigned integer;
— in version number 2.0, two additional data types are available for data storage: a 1-byte signed integer
and a 4-byte floating point.
A list of all parts in the ISO 25178 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
oSIST prEN ISO 25178-71:2025
ISO/DIS 25178-71:2025(en)
Introduction
This document is a geometrical product specification standard and is to be regarded as a general GPS
standard (see ISO 14638). It influences the chain link F and chain link G of the chains of standards on profile
and areal surface texture.
The ISO GPS matrix model given in ISO 14638 gives an overview of the ISO GPS system of which this document
is a part. The fundamental rules of ISO GPS given in ISO 8015 apply to this document and the default decision
rules given in ISO 14253-1 apply to the specifications made in accordance with this document, unless
otherwise indicated.
For more detailed information of the relation of this document to the GPS matrix model, see Annex B.
This document is concerned with software gauges (Type S1) and reference software (Type S2). It defines the
surface data file (SDF) format for Type S1 software gauges.
The SDF format is already used by the industry, in particular, by instrument manufacturers and academia.
The basic concept of the SDF format was originally developed for tactile measuring instruments as part of
[8]
the European Surfstand project and EUR 15178 .

v
oSIST prEN ISO 25178-71:2025
oSIST prEN ISO 25178-71:2025
DRAFT International Standard ISO/DIS 25178-71:2025(en)
Geometrical product specifications (GPS) — Surface
texture: Areal —
Part 71:
Software measurement standards
1 Scope
This document specifies Type S1 and Type S2 software measurement standards for verifying the software of
measuring instruments. It also specifies the surface data file (SDF) format of Type S1 software measurement
standards for the calibration of instruments for the measurement of surface texture by the areal method as
defined in the areal surface texture chain of standards, chain link G. The SDF format is suitable for areal
topography measurement data extracted with an orthogonal grid (see ISO 14406:2010, 5.2) and equidistant
sampling intervals, regardless of the measurement principle.
NOTE Throughout this document, the term “softgauge” is used as a substitute for “software measurement
standard Type S1”.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms (VIM)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC Guide 99, and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
software measurement standard
reference data or reference software intended to reproduce the value of a measurand with known
specification uncertainty in order to verify the software used to calculate the value of a measurand
3.2
ASCII
7-bit character encoding which is congruent with UTF-8 encoding in the first 128 characters
Note 1 to entry: See ISO/IEC 10646.
3.3
uint8
1-byte (8-bit) representation of an unsigned integer
Note 1 to entry: The value range of ”uint8” is from 0 to 255 .

oSIST prEN ISO 25178-71:2025
ISO/DIS 25178-71:2025(en)
Note 2 to entry: In version number 1.0 of the SDF format, the term BYTE was used instead of uint8.
3.4
int8
1-byte (8-bit) representation of a signed integer
Note 1 to entry: The value range of “int8” is from −128 to 127.
3.5
uint16
2-byte representation of an unsigned integer
Note 1 to entry: The value range of “uint16” is from 0 to 65 535.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[9]
“little endian” concept .
3.6
int16
2-byte representation of a signed integer
Note 1 to entry: The value range of “int16” is from −32 768 to 35 767.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[9]
“little endian” concept .
3.7
uint32
4-byte representation of an unsigned integer
Note 1 to entry: The value range of “uint32” is from 0 to 4 294 967 295.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[9]
“little endian” concept .
3.8
int32
4-byte representation of a signed integer
Note 1 to entry: The value range of “int32” is from −2 147 483 648 to 2 147 483 647.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[9]
“little endian” concept .
3.9
binary32
4-byte single precision representation of a normalized floating point number according to IEEE 754
38 38
Note 1 to entry: The value range of “binary32” is from −×3,402 823466 10 to 3,402 823466×10 .
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[9]
“little endian” concept .
Note 3 to entry: Many programming languages support the 4-byte single precision representation in accordance with
IEEE 754. However, alternative terms are often used instead of “binary32”. For example, “float” in C and C++.
Note 4 to entry: The ASCII representation of a “binary32” number not equal to zero, see Figure 1, shall be a normalized
signed floating point number in scientific notation with 7 significant digits and a signed two digit exponent in the
range from −38 to +38. If the “binary32” number is equal to zero, the format “0.000000e+00” shall be used.

oSIST prEN ISO 25178-71:2025
ISO/DIS 25178-71:2025(en)
Key
A
sign for the fraction (“+ ” is optional)
B floating point number in the range [1,0: 10,0] with one digit before and 6 digits after the decimal point
C symbol for the exponent (“e” or “E”)
D
sign for the exponent (“+ ” or “− “ is mandatory)
E integer number in the range [0: 38]
Figure 1 — ASCII representation of “binary32” number

3.10
binary64
8-byte double precision representation of a normalized floating point number according to IEEE 754
Note 1 to entry: The value range of “binary64” is from −×1,797 693  134862315 810 to
1,797 693  134862315 ×810 .
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[9]
“little endian” concept .
Note 3 to entry: In version number 1.0 of the SDF format, the term “DOUBLE” was used instead of “binary64”.
Note 4 to entry: Many programming languages support the 8-byte double precision representation in accordance with
IEEE 754. However, alternative terms are often used instead of “binary64”. For example, “double” in C and C++.
Note 5 to entry: The ASCII representation of a “bi
...