EN ISO 25378:2011
(Main)Geometrical product specifications (GPS) - Characteristics and conditions - Definitions (ISO 25378:2011)
Geometrical product specifications (GPS) - Characteristics and conditions - Definitions (ISO 25378:2011)
ISO 25378:2011 defines general terms for geometrical specifications, characteristics and conditions. These definitions are based on concepts developed in ISO 17450-1 and ISO 22432 and they are given by using a mathematical description based on Annex B of ISO 17450-1:2011.
ISO 25378:2011 is not intended for industrial use as such among designers, but is aimed to serve as the "road map" mapping out the requirements based on geometrical features, thus enabling future standardization for industry and software makers in a consistent manner.
ISO 25378:2011 defines general types of geometrical characteristics and conditions which can be used in GPS. These descriptions are applicable to
a workpiece,
an assembly,
a population of workpieces, and
a population of assemblies.
These definitions are based on concepts of operators and the duality principle contained in ISO 17450-1 and ISO/TS 17450-2 and on the description of types of geometrical features defined in ISO 22432.
Conceptually, these specification operators can be used as specification operators or as verification operators (duality principle).
ISO 25378:2011 is not intended to define GPS specifications, symbology or other types of expression.
Geometrische Produktspezifikation (GPS) - Merkmale und Bedingungen - Begriffe (ISO 25378:2011)
Diese Internationale Norm legt die allgemeinen Begriffe für die geometrischen Spezifikationen, Merkmale und
Bedingungen fest. Diese Definitionen beruhen auf Konzepten, die in ISO 17450-1 und ISO 22432 entwickelt
wurden und sie werden unter Verwendung einer mathematischen Beschreibung angegeben, die auf dem
Anhang B von ISO 17450-1:2011 beruht.
Diese Internationale Norm als solche ist nicht für den industriellen Einsatz unter Konstrukteuren gedacht,
sondern zielt darauf ab, als „Road-Map“ für die Beschreibung der auf Geometrieelementen beruhenden
Anforderungen zu dienen, um so eine zukünftige Normung für die Industrie und die Software-Hersteller in
einer konsistenten Art und Weise zu ermöglichen.
Diese Internationale Norm legt allgemeine Arten von geometrischen Merkmalen und Bedingungen fest, die in
der geometrischen Produktspezifikation verwendet werden können. Diese Beschreibungen sind anwendbar
für
⎯ ein Werkstück,
⎯ eine Baugruppe,
⎯ eine Grundgesamtheit von Werkstücken und
⎯ eine Grundgesamtheit von Baugruppen.
Diese Definitionen beruhen auf den Konzepten von Operatoren und dem in ISO 17450-1 und ISO/TS 17450-2
enthaltenen Dualitätsprinzip, sowie auf der Beschreibung der Arten von Geometrieelementen, die in
ISO 22432 festgelegt sind.
Konzeptionell können diese Spezifikationsoperatoren als Spezifikationsoperatoren oder als
Verifikationsoperatoren verwendet werden (Dualitätsprinzip).
Diese Internationale Norm beabsichtigt nicht, GPS-Spezifikationen, Symbolik oder andere Formen des
Ausdrucks festzulegen
Spécification géométrique des produits - Caractéristiques et conditions - Définitions (ISO 25378:2011)
L'ISO 25378:2011 définit les termes généraux relatifs aux spécifications, caractéristiques et conditions géométriques. Ces définitions reposent sur des concepts développés dans l'ISO 17450‑1 et l'ISO 22432. Elles sont accompagnées d'une description mathématique basée sur l'Annexe B de l'ISO 17450‑1:2011.
L'ISO 25378:2011 n'est pas destinée à un usage industriel en l'état par les concepteurs. Elle fait office de «carte routière» mettant en évidence les exigences reposant sur les fonctions géométriques, permettant ainsi de concevoir de manière cohérente une future normalisation destinée aux industriels et aux fabricants de logiciels.
L'ISO 25378:2011 définit les types généraux de caractéristiques et conditions qui peuvent être utilisés en GPS. Ces descriptions sont applicables
à la pièce,
à un assemblage,
à une population de pièces, et
à une population d'assemblages.
Ces définitions s'appuient sur les concepts des opérateurs et du principe de dualité définis dans l'ISO 17450‑1 et l'ISO/TS 17450‑2 et sur les descriptions des éléments géométriques données dans l'ISO 22432.
De manière conceptuelle, ces opérateurs de spécification peuvent être utilisés comme des opérateurs de spécification ou des opérateurs de vérification (principe de dualité).
L'ISO 25378:2011 n'a pas pour but de définir les spécifications GPS, leurs symboles ou d'autres types d'expressions.
Specifikacija geometrijskih veličin izdelka - Značilnosti in razmere - Definicije (ISO 25378:2011)
Ta mednarodni standard opredeljuje splošno terminologijo za geometrijske specifikacije, značilnosti in razmere.
Definicije so zasnovane na konceptih, razvitih v ISO 17450-1 in ISO 22432, in so podane z uporabo matematičnega opisa na osnovi dodatka B ISO 17450-1:2011.
Ta mednarodni standard kot tak ni namenjen industrijski uporabi pri načrtovalcih, pač pa naj se uporablja kot »zemljevid«, ki orisuje zahteve na osnovi geometrijskih lastnosti, in s tem dosledno omogoča prihodnjo standardizacijo za industrijo in izdelovalce programske opreme.
Ta mednarodni standard opredeljuje splošne tipe geometrijskih značilnosti in razmer, ki se lahko uporabljajo pri GPS. Ti opisi veljajo za
⎯ izdelek,
⎯ sestav,
⎯ množico izdelkov in
⎯ množico sestavov.
Te definicije temeljijo na konceptih operatorjev in načelu dvojnosti iz ISO 17450-1 in ISO/TS 17450-2 ter na opisu tipov geometrijskih značilnosti, opredeljenih v ISO 22432.
Konceptualno se specifikacijski operatorji lahko uporabljajo kot specifikacijski operatorji ali kot overitveni operatorji (načelo dvojnosti).
Ta mednarodni standard ni namenjen opredelitvi specifikacij GPS, simbologije ali drugih vrst izražanja.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2011
6SHFLILNDFLMDJHRPHWULMVNLKYHOLþLQL]GHOND=QDþLOQRVWLLQUD]PHUH'HILQLFLMH ,62
Geometrical product specifications (GPS) - Characteristics and conditions - Definitions
(ISO 25378:2011)
Geometrische Produktspezifikation (GPS) - Merkmale und Bedingungen - Begriffe (ISO
25378:2011)
Spécification géométrique des produits - Caractéristiques et conditions - Définitions (ISO
25378:2011)
Ta slovenski standard je istoveten z: EN ISO 25378:2011
ICS:
17.040.40 6SHFLILNDFLMDJHRPHWULMVNLK Geometrical Product
YHOLþLQL]GHOND *36 Specification (GPS)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN ISO 25378
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2011
ICS 17.040.01
English Version
Geometrical product specifications (GPS) - Characteristics and
conditions - Definitions (ISO 25378:2011)
Spécification géométrique des produits - Caractéristiques Geometrische Produktspezifikation (GPS) - Merkmale und
et conditions - Définitions (ISO 25378:2011) Bedingungen - Begriffe (ISO 25378:2011)
This European Standard was approved by CEN on 7 August 2010.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 25378:2011: E
worldwide for CEN national Members.
Contents Page
Foreword .3
Foreword
This document (EN ISO 25378:2011) has been prepared by Technical Committee ISO/TC 213 "Dimensional
and geometrical product specifications and verification" in collaboration with Technical Committee
CEN/TC 290 “Dimensional and geometrical product specification and verification” the secretariat of which is
held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by October 2011, and conflicting national standards shall be withdrawn at
the latest by October 2011.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 25378:2011 has been approved by CEN as a EN ISO 25378:2011 without any modification.
INTERNATIONAL ISO
STANDARD 25378
First edition
2011-04-01
Geometrical product specifications
(GPS) — Characteristics and
conditions — Definitions
Spécification géométrique des produits — Caractéristiques et
conditions — Définitions
Reference number
ISO 25378:2011(E)
©
ISO 2011
ISO 25378:2011(E)
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ii © ISO 2011 – All rights reserved
ISO 25378:2011(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 General presentation.15
4.1 General principles of the specifications .15
4.2 General principle of the characteristics.15
5 Illustration of GPS characteristics.16
5.1 General .16
5.2 Single and relationship characteristics .17
5.3 Local and global characteristics.20
5.4 Deviated and reference feature.20
5.5 Independent characteristics.21
5.6 Zone characteristic.30
5.7 Gauge characteristic.34
5.8 Assembly or sub-assembly characteristic .39
6 Relations between terms related to characteristic .44
Annex A (informative) Overview diagrams.46
Annex B (normative) Basic (geometrical) characteristic.49
Annex C (informative) Relation to the GPS matrix model.57
Bibliography.58
ISO 25378:2011(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 25378 was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product
specifications and verification.
iv © ISO 2011 – All rights reserved
ISO 25378:2011(E)
Introduction
This International Standard is a Geometrical product specifications (GPS) standard and is to be regarded as a
global GPS standard (see ISO/TR 14638). It influences all chain links of all chains of standards in the general
GPS matrix.
To facilitate the reading and the understanding of this International Standard, it is essential to refer to
ISO 17450-1 and ISO/TS 17450-2.
Geometrical characteristics exist in three “worlds”:
⎯ the world of nominal geometrical definition, where an ideal representation of the future workpiece is
defined by the designer;
⎯ the world of specification, where several representations of the future workpiece are imagined by the
designer;
⎯ the world of verification, where one or several representations of a given workpiece are identified in the
application of measuring procedure(s).
A GPS specification defines requirements through a geometrical characteristic and condition.
In the world of verification, mathematical operations can be distinguished from physical operations. The
physical operations are the operations based on physical procedures; they are generally mechanical, optical
or electromagnetic. The mathematical operations are mathematical treatments of the sampling of the
workpiece. This treatment is generally achieved by computing or electronic treatment.
It is important to understand the relationship between these three worlds.
These specifications, characteristics and conditions, generically defined in this International Standard, are well
suited to define requirements of rigid parts and assemblies and can also be applied to non-rigid parts and
assemblies.
INTERNATIONAL STANDARD ISO 25378:2011(E)
Geometrical product specifications (GPS) — Characteristics
and conditions — Definitions
1 Scope
This International Standard defines general terms for geometrical specifications, characteristics and conditions.
These definitions are based on concepts developed in ISO 17450-1 and ISO 22432 and they are given by
using a mathematical description based on Annex B of ISO 17450-1:2011.
This International Standard is not intended for industrial use as such among designers, but is aimed to serve
as the “road map” mapping out the requirements based on geometrical features, thus enabling future
standardization for industry and software makers in a consistent manner.
This International Standard defines general types of geometrical characteristics and conditions which can be
used in GPS. These descriptions are applicable to
⎯ a workpiece,
⎯ an assembly,
⎯ a population of workpieces, and
⎯ a population of assemblies.
These definitions are based on concepts of operators and the duality principle contained in ISO 17450-1 and
ISO/TS 17450-2 and on the description of types of geometrical features defined in ISO 22432.
Conceptually, these specification operators can be used as specification operators or as verification operators
(duality principle).
This International Standard is not intended to define GPS specifications, symbology or other types of
expression.
2 Normative references
The following referenced documents are indispensable for the application 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 3534-1:2006, Statistics — Vocabulary and symbols — Part 1: General statistical terms and terms used in
probability
ISO 3534-2, Statistics — Vocabulary and symbols — Part 2: Applied statistics
ISO 17450-1:2011, Geometrical product specifications (GPS) — General concepts — Part 1: Model for
geometrical specification and verification
ISO/TS 17450-2, Geometrical product specifications (GPS) — General concepts — Part 2: Basic tenets,
specifications, operators and uncertainties
ISO 25378:2011(E)
1)
ISO 22432 , Geometrical product specifications (GPS) — Features utilized in specification and verification
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3534-1, ISO 3534-2 and
ISO 17450-1 and the following apply.
3.1
geometrical specification
expression of a set of one or more conditions on one or more geometrical characteristics
NOTE 1 A specification can express a combination of individual conditions on an individual characteristic or a
population condition on a population characteristic.
NOTE 2 A specification consists of one or more single specifications. These single specifications can be individual
specifications, population specifications or any combination.
3.2
condition
combination of a limit value and a binary relational mathematical operator
EXAMPLE 1 “be less than or equal to 6,3”, the expression of this condition can be, for instance: 6,3 max or U 6,3.
Mathematically: let X be the considered value of the characteristic, the condition is X u 6,3.
EXAMPLE 2 “be greater than or equal to 0,8”, the expression of this condition can be, for instance: 0,8 min or L 0,8.
Mathematically: let X be the considered value of the characteristic, the condition is 0,8 u X.
EXAMPLE 3 a set of two complementary conditions (lower and upper limits) can be expressed through, for instance:
+0,4 +0,3
10,2 − 9,8, 9,8 , 10 ± 0,2, or 9,9 . Mathematically: let X be the considered value of the characteristic, the condition
0 −0,1
is 9,8 u X u 10,2.
2 2
EXAMPLE 4 “be less than or equal to R, R being given by a function, R = (X + Y ) × 0,85, X and Y being the ordinates
of the coordinate system.
NOTE 1 A binary relational mathematical operator is a mathematical concept which generalizes the notion as “greater
than or equal to” in arithmetic, or “is item of the set” in set theory.
NOTE 2 The limit value can be defined for any individual workpiece or for populations of workpieces.
NOTE 3 The limit value can be independent of a coordinate system or dependent upon it. In the latter case, the limit
value depends on the function of the ordinates of the coordinate system or graphical ordinate system.
NOTE 4 The limit value can be determined by a statistical tolerancing approach, by an arithmetical tolerancing (worst
case) approach or by other means. The manner of determining the limit value and the choice of condition is not the subject
of this International Standard.
NOTE 5 Two possible inequality relations exist:
⎯ the characteristic value can be less than or equal to the limit value (upper limit);
⎯ the characteristic value can be greater than or equal to the limit value (lower limit).
1) In preparation.
2 © ISO 2011 – All rights reserved
ISO 25378:2011(E)
3.2.1
individual condition
condition where the limit value applies to any value of an individual characteristic coming from any workpiece
EXAMPLE An individual condition used in an individual specification: the individual characteristic value shall be less
than or equal to 10,2. Mathematically: let X be the considered value of the individual characteristic, the condition is
X u 10,2.
NOTE An individual condition can be used alone or in combination with a population condition on the corresponding
population characteristic.
3.2.2
population condition
condition where the limits apply to the value of the population characteristic
EXAMPLE A population condition used in a population specification: the value of a population characteristic shall be
less than or equal to 10,1. Mathematically: let X be the considered value of the population characteristic (mean value of
the population of global individual characteristic values), the condition is Xu10,1.
NOTE The population condition can be used for statistical process control (SPC).
3.3
geometrical characteristic
individual characteristic or population characteristic related to the geometry
NOTE 1 This International Standard applies to the field of geometry and therefore, throughout this standard, only
“geometrical characteristics” are used. The term “characteristic” is defined in ISO 9000:2005, 3.5.1.
NOTE 2 The geometrical characteristic permits the evaluation of a quantity which could be associated to, for instance,
an angular dimension, a linear dimension, an area, a volume, etc.
3.3.1
individual characteristic
individual geometrical characteristic
single geometrical property of one or more geometrical features belonging to a workpiece
EXAMPLE The two-point diameter is an individual characteristic and the result is mathematically varying along the
cylindrical feature: it is a local individual characteristic. The minimum circumscribed cylinder diameter is an individual
characteristic and the result is mathematically unique: it is a global individual characteristic.
NOTE 1 A local characteristic can be single or calculated.
NOTE 2 The evaluation of an individual characteristic does not necessarily give a unique result (it can be characterized
as a local individual characteristic or a global individual characteristic).
3.3.1.1
local individual characteristic
individual characteristic of which the result of evaluation is not unique
EXAMPLE 1 The two-point diameter is an individual characteristic and the result varies mathematically along the
cylindrical feature: it is a local individual characteristic.
EXAMPLE 2 See 5.3.
NOTE 1 A local individual characteristic is evaluated on portion feature(s) and can be a direct characteristic or a
calculated characteristic. The local diameter measured between two points is a direct local characteristic. The mean of
local diameters measured between two points for a given section is a calculated local characteristic.
NOTE 2 The result of an evaluation is related to an entire feature; a single two-point diameter is in itself unique.
ISO 25378:2011(E)
3.3.1.2
global individual characteristic
individual characteristic of which the result of evaluation is unique
EXAMPLE 1 The minimum circumscribed cylinder diameter is a direct global individual characteristic (the result is
mathematically unique).
EXAMPLE 2 The maximum of two-point diameters along a given cylinder is a calculated global individual characteristic
(the result comes from a statistic and is mathematically unique).
NOTE The result of evaluation of a global individual characteristic can come from a unique evaluation or a statistic of
a set of results of evaluation of a local individual characteristic, characterized as direct and calculated, respectively.
3.3.2
population characteristic
statistic defined from the characteristic values, obtained on the population of workpieces or the population of
assemblies
NOTE 1 Population characteristics are used to consider a total population of workpieces.
EXAMPLE 1 The arithmetic mean or the standard deviation on the population of workpieces of a global individual
characteristic are population characteristics.
NOTE 2 Population characteristics are only statistically meaningful for GPS characteristics when the value is the result
of global individual characteristics.
EXAMPLE 2 The minimum circumscribed cylinder diameter has one unique value for a given cylindrical feature.
Therefore, a population characteristic based on this individual characteristic value will be statistically meaningful. The two-
point diameter for a given cylindrical feature will vary within a range, dependent upon the form deviations of the feature. In
this case, a population characteristic cannot be defined from the population of values. It could be possible, in this case, to
establish a population characteristic from the maximum value of the two-point diameter along the feature. In this case, the
individual characteristic is a global individual characteristic which is the maximum two-point diameter on a given workpiece.
NOTE 3 The population characteristic can be used, for example, for statistical process control (SPC).
3.4
statistic
completely specified function of random variables
EXAMPLE See Table 1. More information can be found in the ISO 3534 series.
NOTE 1 This definition, taken from ISO 3534-1:2006, 1.8, is associated to notes which are not reproduced in this
International Standard.
NOTE 2 In GPS, the random variables which are used are, in most cases, one-dimensional (scalar). Multidimensional
(vector) variables also exist.
NOTE 3 For a population or a sample of individual characteristic values, at least one statistic can be applied. In GPS, a
statistic can be used on a population of local individual characteristic values taken on one workpiece, or on a population of
global individual characteristic values taken on a population of workpieces.
4 © ISO 2011 – All rights reserved
ISO 25378:2011(E)
Table 1 — Non-exhaustive list of statistics
a
Description of the statistic
Mathematical description according to ISO 3534-1
the minimum minimum (X)
the maximum maximum (X)
n
the expected value (mean)
kk
μ==EX() X , or
∑ i
n
i=1
μ==Eg()X g()Xdp= g(x)dF(x)
⎡⎤
⎣⎦
∫∫
µ− TV
the difference between the average and the target value (TV)
the standard deviation σ= VX()
the variance
VX()=−E⎡X E()X ⎤
⎣ ⎦
a
Where X is the characteristic value.
NOTE 4 For some statistical applications (like SPC), it can be necessary to define a “Target Value” (see ISO 7966 and
ISO 3534-2).
3.5
calculated characteristic
local or global individual characteristic obtained from a collection of a set of values of one local individual
characteristic by using a function and not changing the nature of the initial characteristic
EXAMPLE 1 The normal vector obtained from three local individual characteristic vector values is a calculated
characteristic, which is a local individual characteristic (see Figure 1).
EXAMPLE 2 The expected value (mean value) obtained from the population of values of local diameter of the cylinder
in a specific section is a local individual characteristic.
EXAMPLE 3 The expected value (mean value) obtained from the population of values of local diameter of the cylinder
(taking into account the entire cylinder) is a global individual characteristic.
Key
R , R , R local individual characteristic vector values in a coordinate system
1 2 3
C coordinates assigned to the normal vector of the surface
i
JJG
V normal vector of the surface
i
Figure 1 — Calculated characteristic consisting of the angles of a normal vector of a surface
coming from three values of a local individual characteristic
ISO 25378:2011(E)
3.5.1
direct characteristic
local or global characteristic derived from a single evaluation
3.5.2
transformed characteristic
local or global characteristic which changes the initial characteristic
3.6
combination characteristic
geometrical characteristic obtained from a collection of values related to a set of geometrical characteristics by
using a function
EXAMPLE The volume of a cylinder can be seen as a combination characteristic which is a function of two
geometrical characteristic values: the length and the diameter of the cylinder.
3.7
value of a geometrical characteristic
geometrical characteristic value
signed value with or without a unit resulting from an evaluation of a geometrical characteristic, quantified on a
workpiece or the population of workpieces
NOTE The characteristic value is, in most cases, a uni-dimensional value but can be multidimensional (vector value).
EXAMPLE Local two-point diameter, global minimum circumscribed diameter, vector describing the location and
orientation of a hole axis.
3.7.1
value of an individual characteristic
signed value with or without a unit resulting from an evaluation of an individual characteristic, quantified on
one workpiece
3.7.2
value of a population characteristic
signed value with or without a unit resulting from an evaluation of a population characteristic, quantified on the
population of workpieces
NOTE 1 By using sampling (instead of the whole population), a sampling uncertainty is introduced (see E.4 of
ISO/IEC Guide 98-3:2008).
NOTE 2 The evaluation of a population characteristic is a two-step process:
⎯ evaluation of a set of results of an individual characteristic;
⎯ statistical evaluation of the results of step 1.
NOTE 3 For any individual characteristic value, the value obtained from a simplified verification operator will, in general,
differ from the value obtained from a perfect verification operator. In general, there is no simple way to estimate the
variation of this difference and, in most practical cases, it is simply impossible. It is not unusual for this difference to be of
the same magnitude as the population variation. The variation in the difference may increase or decrease the evaluated
population variation. Because this difference enters into the statistical calculation and affects it in such a significant and
unpredictable way, a meaningful estimation of the uncertainty of the evaluation of the variation of a characteristic in a
population by a simplified verification operator is, in general, very difficult and in most cases impossible. Therefore, it is
only meaningful to use population characteristics in specifications that will be evaluated by verification operators without
method uncertainty.
EXAMPLE 1 It is impossible to define the relationship between the standard deviation of two-point diameters on a
population of workpieces and the standard deviation of the minimum circumscribed cylinder diameter of the same
population of workpieces without complete knowledge of the form deviations of the workpieces and the locations of the
two-point diameters.
EXAMPLE 2 Average length of a population of rods: 5,342 mm (where the length is defined as the distance between
two parallel planes between which each rod fits).
6 © ISO 2011 – All rights reserved
ISO 25378:2011(E)
3.7.3
variation characteristic
set of local individual characteristic values recorded along a feature
NOTE 1 A characteristic variation may or may not be related to a coordinate system.
NOTE 2 To obtain a curve of the variation of characteristic values, it is necessary to define a coordinate system.
NOTE 3 To obtain the dispersion of the variation, it is not necessary to define a coordinate system.
EXAMPLE 1 The minimum circumscribed circle diameter along the cylinder is a local individual characteristic. By
considering a coordinate system link with the axis of the associated cylinder, it is possible to follow the variation of these
local individual characteristic values (see Figure 2).
Key
1 real feature
2 local characteristic values
a
Associated cylinder.
b
Associated plane.
c
Coordinate system.
Figure 2 — Example of curve of characteristic-values variation,
based on minimum circumscribed circle diameter
EXAMPLE 2 In the case of texture characteristics, it can be necessary to use several types of curve of characteristic-
values variation or a transformation of it (see Figure 3).
ISO 25378:2011(E)
a) Variation curve of situation characteristic between the non-ideal integral surface and a reference feature
b) Curve of characteristic-values variation corresponding to the transformation of curve a) by an application of a
rotation with an objection function after application of a filter
c) Curve of ratios corresponding to the transformation of curve b) to define the ratio of material
Figure 3 — Examples of curves of characteristic-values variation
3.7.3.1
variation curve
characteristic variation represented in a coordinate system
NOTE 1 A variation curve can be obtained without transformation or by mathematical transformation. It can be qualified
as direct or transformed.
NOTE 2 A variation curve can be filtered.
3.8
basic characteristic
basic geometrical characteristic
intrinsic characteristic or situation characteristic
NOTE 1 A basic characteristic does not include the definition of intermediate features obtained by operations.
NOTE 2 See Annex B.
3.8.1
intrinsic characteristic
characteristic of an ideal feature
[ISO 17450-1:2011, 3.14]
NOTE 1 A plane, a straight line and a point have no intrinsic characteristic.
8 © ISO 2011 – All rights reserved
ISO 25378:2011(E)
EXAMPLE The diameter is the intrinsic characteristic of a cylinder. A torus has two intrinsic characteristics: the
diameter of the generatrix and the diameter of the directrix. A cylinder and a torus are examples of features of size. The
size of the feature of size of type cylinder is its diameter. The size of the feature of size of type torus is the diameter of the
generatrix.
NOTE 2 See B.2.
3.8.2
situation characteristic
characteristic defining the relative location or orientation between two features
[ISO 17450-1:2011, 3.23]
NOTE 1 A situation characteristic is an orientation characteristic or a location characteristic.
NOTE 2 See B.3.
3.8.2.1
orientation characteristic
geometrical characteristic defining the related orientation between two ideal features
NOTE See B.3.2.
3.8.2.2
location characteristic
geometrical characteristic defining the related location between two features
NOTE A situation characteristic defines the related location between two ideal features (see B.3.2), between a
feature portion and an ideal feature (see B.3.3), between a non-ideal feature and an ideal feature (see B.3.4), and
between two non-ideal features (see B.3.5).
3.9
GPS characteristic
geometrical characteristic intended to be standardized corresponding to micro- or macro-geometry which may
be quantified
NOTE See Clause 5.
3.9.1
input feature
GPS characteristic input feature
set of one or more features coming from the surface model or real surfaces of the workpiece which may be
filtered, from which a GPS characteristic is defined
3.9.1.1
single characteristic
single individual characteristic
geometrical characteristic describing the micro- or macro-geometry of a feature taken from one workpiece
NOTE 1 The considered feature can be identified by a collection of several features, such as a feature constituted by
two straight lines or a feature constituted by four parallel cylinders.
NOTE 2 See 5.2.1.
3.9.1.2
relationship individual characteristic
individual geometrical characteristic describing the geometrical situation (orientation, position) between
several geometrical features
NOTE See 5.2.2.
ISO 25378:2011(E)
3.9.1.3
deviated feature
geometrical feature or variation curve considered in an intrinsic characteristic or which has the larger deviation
among the two features considered in a situation characteristic
NOTE See 5.4.
3.9.1.4
reference feature
geometrical feature or variation curve which has the smaller deviation among the two features considered in a
situation characteristic
NOTE See 5.4.
3.9.1.5
facing feature
ideal feature simulating the feature which a given feature on a workpiece is interfacing with by considering the
assembly or some virtual geometry
NOTE 1 A facing feature cannot be defined alone.
NOTE 2 The facing feature can have the same nominal geometry of the nominal integral feature (depending on the
function). See Table 2.
NOTE 3 A facing feature can simulate the orientation or location of a workpiece, simulate a fitting, etc.
NOTE 4 It is sometimes necessary to consider the interface between the integral feature and its facing feature to
precisely define the intrinsic characteristic or the relationship characteristic.
10 © ISO 2011 – All rights reserved
ISO 25378:2011(E)
Table 2 — Examples of interfaces between an internal cylinder and different facing features
Assembly Facing feature with the internal Interface
cylinder as considered
workpiece
Cylinder Cylinder
Cylinder/Cylinder
Sphere
Cylinder/Sphere
Circle
Cylinder/Torus
Torus
Cylinder/Set of two spheres
Two points
Set of two spheres
3.9.2
independent characteristic
geometrical characteristic which has no influence on, nor is influenced by, any other geometrical characteristic
NOTE See 5.5.
3.9.2.1
independent form characteristic
GPS characteristic defining the deviation of form of a non-ideal feature (which may be a derived or integral
feature) as a situation characteristic
NOTE 1 The reference feature is a substitute feature obtained from the deviated feature by an association.
NOTE 2 See 5.5.2.
ISO 25378:2011(E)
3.9.2.2
independent size characteristic
GPS characteristic defining the size of a non-ideal feature (which may be a derived or integral feature) as an
intrinsic characteristic
NOTE 1 The deviated feature is the reference feature of the independent form characteristic.
NOTE 2 See 5.5.3.
3.9.2.3
independent orientation characteristic
GPS characteristic defining the deviation of orientation between non-ideal features (which may be a derived or
integral feature) as a situation characteristic
NOTE 1 The deviated features are the reference features of the independent form characteristics of each of the
features.
NOTE 2 The reference features are ideal features obtained from the deviated features by an association with
constraints of orientation.
NOTE 3 See 5.5.4.
3.9.2.4
independent location characteristic
GPS characteristic defining the deviation of location between non-ideal features (which may be a derived or
integral feature) as a situation characteristic
NOTE 1 The deviated features are the reference features of the independent orientation characteristic.
NOTE 2 The reference features are ideal features obtained from the deviated features by an association with
constraints of orientation and location.
NOTE 3 See 5.5.5.
3.9.2.5
complementary characteristic
set of independent characteristics related to form, size, orientation and location
NOTE See 5.5.
3.9.3
zone characteristic
GPS characteristic defining the deviation of non-ideal feature(s) [which may be a derived or integral feature(s)]
as a situation characteristic of type maximum distance
NOTE See 5.6.
3.9.3.1
zone form characteristic
zone characteristic defining the deviation of form of a non-ideal feature (which may be a derived or integral
feature)
NOTE 1 The deviated feature is the non-ideal feature itself or a feature obtained from it by filtration.
NOTE 2 The reference feature is a substitute feature obtained from the deviated feature by an association, with or
without feature-size constraint.
NOTE 3 See 5.6.2.
12 © ISO 2011 – All rights reserved
ISO 25378:2011(E)
3.9.3.2
zone orientation characteristic
zone characteristic defining the deviation of orientation of non-ideal features (which may be a derived or
integral feature)
NOTE 1 The deviated features are the non-ideal features themselves or features obtained from them by filtration
(smoothed features) or by association (substitute features).
NOTE 2 The reference features are features obtained from the deviated features by an association (substitute
features) with constraints of orientation, with or without feature-size constraint.
NOTE 3 See 5.6.3.
3.9.3.3
zone location characteristic
zone characteristic defining the deviation of location of non-ideal features (which may be a derived or integral
feature)
NOTE 1 The deviated features are the non-ideal features themselves or features obtained from them by filtration
(smoothed features) or by association (substitute features).
NOTE 2 The reference features are features obtained from the deviated features by an association (substitute
features) with constraints of orientation and location, with or without feature-size constraint.
NOTE 3 See 5.6.4.
3.9.4
gauge characteristic
GPS characteristic defining the deviation of integral or smoothed feature(s) as a basic characteristic, taking
into account at least one candidate feature associated to the input features
NOTE See 5.7.
3.9.4.1
gauge size characteristic
GPS characteristic defining the size of a deviated feature, utilizing the relevant facing feature given the
simulated interface of the non-ideal integral feature or smoothed feature
NOTE 1 In the majority of cases, the types of the facing feature and the integral feature are the same. Where this is the
case, there is, nominally, no difference between the interface and the integral feature.
NOTE 2 For example, the gauge size characteristic integrates the notion of diameter of associated cylinders and local
diameter.
NOTE 3 See 5.7.2.
3.9.4.2
gauge variation characteristic
GPS characteristic defining the deviation of integral or smoothed feature(s) as a situation characteristic
between a reference feature and candidate feature(s) associated to the integral feature(s) with an objective of
minimum or maximum of the situation characteristic
NOTE 1 The reference feature is relevant to the concept of datum.
NOTE 2 See 5.7.3.
3.9.4.3
gauge gap characteristic
GPS characteristic defining the deviation of integral or smoothed feature(s) as a situation characteristic
between two orientations and/or locations of a candidate feature such that the situation characteristic is a
maximum.
NOTE See 5.7.4.
ISO 25378:2011(E)
3.9.4.4
floating contact
contact which permits tangential, normal and rotative related movements during regular functioning
NOTE See 5.8.2.
3.9.4.5
slipping contact
contact constrained by a mechanical action which permits only tangential related movement during regular
functioning
NOTE See 5.8.2.
3.9.4.6
rolling contact
contact which permits only rotative related movements during regular functioning
NOTE See 5.8.2.
3.9.4.7
rolling/slipping contact
contact which permits tangential and rotative related movements during regular functioning
NOTE See 5.8.2.
3.9.4.8
fixed contact
contact constrained by a mechanical action and/or an induced friction which does not permit related
movement during regular functioning
NOTE See 5.8.2.
3.9.4.9
configuration
particular positioning of the parts of an assembly without interference between the parts
NOTE See 5.8.3.
3.9.4.10
subset of configuration
configuration such that the features in fixed contact are in a given position
NOTE See 5.8.3.
3.9.5
texture characteristic
calculated characteristic on a curve of characteristic-values variation, which has been defined primarily on a
portion of a non-ideal integral feature
NOTE 1 The curve of characteristic-values variation can represent the variation of the situation characteristic between
a deviated feature and a reference feature or a transformation.
NOTE 2 The curve of characteristic-values variation can be multidimensional.
14 © ISO 2011 – All rights reserved
ISO 25378:2011(E)
4 General presentation
4.1 General principles of the specifications
A GPS specification corresponds
a) to a requirement:
⎯ on all the workpieces taken individually: individual specification,
⎯ on the population of workpieces, taken collectively: population specification, or
b) to a compound requirement combining the two previous types of requirements.
In the case of a single specification, the condition shall be applied to any characteristic value.
This characteristic is a characteristic on one feature (for example, the form characteristic of a nominally planar
surface) or between several features (for example, the orientation characteristic between two surfaces)
(see ISO 22432).
NOTE This characteristic can be a global characteristic (for example, the diameter of a least-squares cylinder
associated to a nominally cylindrical surface) or a function of a local characteristic (function of the two-point diameter of a
nominally cylindrical surface).
In the case of population specification, the condition shall be applied on the popula
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