Geometrical product specifications (GPS) - Surface texture: Areal - Part 72: XML file format x3p (ISO 25178-72:2017)

ISO 25178-72:2017 defines the XML file format x3p for storage and exchange of topography and profile data.

Geometrische Produktspezifikation (GPS) - Oberflächenbeschaffenheit: Flächenhaft - Teil 72: XML Dateiformat x3p (ISO 25178-72:2017)

Spécification géométrique des produits (GPS) - État de surface: Surfacique - Partie 72: Format de fichier XML x3p (ISO 25178-72:2017)

ISO 25178-72:2017 définit le format de fichier XML x3p pour le stockage et l'échange des données de topographie et de profils.

Specifikacija geometrijskih veličin izdelka (GPS) - Tekstura površine: ravna - 72. del: XML format datoteke x3p (ISO 25178-72:2017)

Ta dokument določa XML format datoteke x3p za shranjevanje in izmenjavo topografskih in profilnih podatkov.

General Information

Status
Published
Publication Date
06-Jun-2017
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
07-Jun-2017
Completion Date
07-Jun-2017

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SLOVENSKI STANDARD
SIST EN ISO 25178-72:2017
01-september-2017

6SHFLILNDFLMDJHRPHWULMVNLKYHOLþLQL]GHOND *36 7HNVWXUDSRYUãLQHUDYQD

GHO;0/IRUPDWGDWRWHNH[S ,62

Geometrical product specifications (GPS) - Surface texture: Areal - Part 72: XML file

format x3p (ISO 25178-72:2017)

Geometrische Produktspezifikation (GPS) - Oberflächenbeschaffenheit: Flächenhaft -

Teil 72: XML Dateiformat x3p (ISO 25178-72:2017)

Spécification géométrique des produits (GPS) - État de surface: Surfacique - Partie 72:

Format de fichier XML x3p (ISO 25178-72:2017)
Ta slovenski standard je istoveten z: EN ISO 25178-72:2017
ICS:
17.040.20 Lastnosti površin Properties of surfaces
17.040.40 6SHFLILNDFLMDJHRPHWULMVNLK Geometrical Product
YHOLþLQL]GHOND *36 Specification (GPS)
SIST EN ISO 25178-72:2017 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 25178-72:2017
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SIST EN ISO 25178-72:2017
EN ISO 25178-72
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2017
EUROPÄISCHE NORM
ICS 17.040.20
English Version
Geometrical product specifications (GPS) - Surface texture:
Areal - Part 72: XML file format x3p (ISO 25178-72:2017)

Spécification géométrique des produits (GPS) - État de Geometrische Produktspezifikation (GPS) -

surface: Surfacique - Partie 72: Format de fichier XML Oberflächenbeschaffenheit: Flächenhaft - Teil 72: XML

x3p (ISO 25178-72:2017) Dateiformat x3p (ISO 25178-72:2017)
This European Standard was approved by CEN on 24 April 2017.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 25178-72:2017 E

worldwide for CEN national Members.
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SIST EN ISO 25178-72:2017
EN ISO 25178-72:2017 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 25178-72:2017
EN ISO 25178-72:2017 (E)
European foreword

This document (EN ISO 25178-72:2017) 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 December 2017, and conflicting national standards

shall be withdrawn at the latest by December 2017.

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, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 25178-72:2017 has been approved by CEN as EN ISO 25178-72:2017 without any

modification.
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SIST EN ISO 25178-72:2017
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SIST EN ISO 25178-72:2017
INTERNATIONAL ISO
STANDARD 25178-72
First edition
2017-05
Geometrical product specifications
(GPS) — Surface texture: Areal —
Part 72:
XML file format x3p
Spécification géométrique des produits (GPS) — État de surface:
Surfacique —
Partie 72: Format de fichier XML x3p
Reference number
ISO 25178-72:2017(E)
ISO 2017
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Requirements .......................................................................................................................................................................................................... 4

4.1 Units ................................................................................................................................................................................................................. 4

4.2 Recommended offset value .......................................................................................................................................................... 4

5 x3p file format ......................................................................................................................................................................................................... 4

5.1 General ........................................................................................................................................................................................................... 4

5.2 File name extension ............................................................................................................................................................................ 4

5.3 Minimum contents of zip-container ..................................................................................................................................... 4

5.4 Optional contents of zip-container ........................................................................................................................................ 4

5.4.1 General...................................................................................................................................................................................... 4

5.4.2 Binary encoded coordinates .................................................................................................................................. 5

5.4.3 Validity mask ....................................................................................................................................................................... 5

5.4.4 Vendor specific extensions ...................................................................................................................................... 5

5.5 Contents and format of main.xml............................................................................................................................................ 5

5.5.1 General...................................................................................................................................................................................... 5

5.5.2 Main records ........................................................................................................................................................................ 5

5.5.3 Record1: Header, data types, and axes definitions ............................................................................. 5

5.5.4 Record2: Meta data ........................................................................................................................................................ 8

5.5.5 Record3: 3D point data............................................................................................................................................10

5.5.6 Record4: Checksum information ....................................................................................................................14

5.5.7 Vendor specific extensions ...................................................................................................................................14

Annex A (informative) XML file format ...........................................................................................................................................................15

Annex B (informative) Sample main.xml ......................................................................................................................................................20

Annex C (informative) Relation with the GPS matrix .......................................................................................................................22

Bibliography .............................................................................................................................................................................................................................23

© ISO 2017 – All rights reserved iii
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(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.

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).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on 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 the following

URL: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product

specifications and verification.
A list of all parts in the ISO 25178 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
Introduction

This document is a geometrical product specification (GPS) standard and is to be regarded as a general

GPS standard (see ISO 14638). It influences the chain link F 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 other standards and the GPS matrix

model, see Annex C.

The x3p format was in use in industry and academia before the creation of this document. The x3p file

format as defined in this document has been developed based on the definitions in ISO 5436-2. The

openGPS consortium provides a free open source software implementation of this file format to

avoid the inevitable inconsistency of multiple proprietary implementations.

1) openGPS is an example of a suitable product available commercially. This information is given for the

convenience of users of this document and does not constitute an endorsement by ISO of this product.

© ISO 2017 – All rights reserved v
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SIST EN ISO 25178-72:2017
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SIST EN ISO 25178-72:2017
INTERNATIONAL STANDARD ISO 25178-72:2017(E)
Geometrical product specifications (GPS) — Surface
texture: Areal —
Part 72:
XML file format x3p
1 Scope

This document defines the XML file format x3p for storage and exchange of topography and profile data.

2 Normative references

The following document is referred to in the text in such a way that some or all of its 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 25178-600 , Geometrical product specifications (GPS) —Surface texture: Areal — Part 600:

Metrological characteristics for areal-topography measuring methods
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 25178-600 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
zip-container

file format that can be used as a container for multiple files and folders that does also support a

compression of the stored content
[1]
Note 1 to entry: The file format description is in the public domain .
3.2
md5

method to calculate a unique 16-byte binary checksum used to check the integrity of files

Note 1 to entry: The binary value is typically represented by 32 hexadecimal digits.

Note 2 to entry: See Reference [2].
3.3
int16
2-byte representation of a signed integer

Note 1 to entry: The int16 type has a minimum value of –32 768 and a maximum value of 32 767.

2) Under preparation. Stage at the time of publication: ISO/DIS 25178-600.
© ISO 2017 – All rights reserved 1
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)

Note 2 to entry: The less significant bytes are stored in memory addresses lower than those in which are stored

the more significant bytes.
3.4
int32
4-byte representation of a signed integer

Note 1 to entry: The int32 type has a minimum value of -2 147 483 648 and a maximum value of 2 147 483 647.

Note 2 to entry: The less significant bytes are stored in memory addresses lower than those in which are stored

the more significant bytes.
3.5
float32
4-byte representation of a floating point number according to IEEE 754
128 128

Note 1 to entry: The float32 type has a minimum value of – 2 and a maximum value of 2 . The smallest

-126
positive number representable is 2 .

Note 2 to entry: The ASCII representation is a signed floating point number with 8 digits and a signed two-digit

exponent in the range [-38.. +38].

Note 3 to entry: The less significant bytes are stored in memory addresses lower than those in which are stored

the more significant bytes.
3.6
float64
8-byte representation of a floating point number according to IEEE 754
1 024 1 024

Note 1 to entry: The float64 type has a minimum value of –2 and a maximum value of 2 . The smallest

-1 022
positive number representable is 2 .

Note 2 to entry: The ASCII representation is a floating point number with 16 digits and a signed three-digit

exponent in the range [- 308.. + 308].

Note 3 to entry: The less significant bytes are stored in memory addresses lower than those in which are stored

the more significant bytes.
3.7
not a number
NaN

special floating point value defined in IEEE 754 specifying a number that is not computable

Note 1 to entry: Some floating point implementations define more than one value for NaN to distinguish between

Quiet NaNs and Signaling NaNs. In this case the Quiet NaN is preferred.

Note 2 to entry: All mathematical operations incorporating a NaN value yield NaN as result. As a consequence, all

comparisons with a NaN value yield “unequal”. This is especially true for the equality comparison of two NaN values.

3.8
element
start tag followed by a data value followed by an end tag

EXAMPLE 1 An element with the name “example” comprising a start and an end tag would be implemented as

contents of element
EXAMPLE 2 An empty element with the name “example” would be implemented as

Note 1 to entry: An element begins with a start tag and ends with an end tag. Alternatively, an element may

consist of an empty tag solely. The content of the element is between the start and end tag and may contain

further elements.
2 © ISO 2017 – All rights reserved
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
3.9
extensible markup language
XML
language for encoding documents electronically
Note 1 to entry: XML is a subset of SGML (see Reference [7]).
3.10
uniform resource locator
URL

character string to locate a resource in a computer network or on a local computer

EXAMPLE A well-known use of a URL is the specification of a web site’s address like “http:// www .iso .org/ ”.

3.11
uniform resource identifier
URI
character string uniquely identifying a name or resource in a hierarchical style

EXAMPLE A URI for this document could be “ www . i s o .org/ ISO _25178 _Part _72”.

Note 1 to entry: A URL is the most common form of a URI.

Note 2 to entry: The relation between a URI and a URL is like the relation between a person’s name (the URI) and

a person’s address (the URL).

Note 3 to entry: To create a unique URI, it is good practice to start a URI with a domain name that has been

registered on the name of the owner.
3.12
offset

distance of the stored geometric data to the origin of the coordinate system along one axis of the

coordinate system
3.13
rotation matrix
3×3 matrix defining the rotation of the data set in 3D space

Note 1 to entry: It defines the orientation of the stored point cloud in 3D space.

3.14
global coordinate system

three-dimensional coordinate system in which the position and orientation of the original point cloud

is defined
3.15
view coordinate system
three-dimensional coordinate system in which the 3D points are defined

Note 1 to entry: In the view coordinate system, the represented surface or point cloud typically is projectable

along one spatial direction.
3.16
data matrix

one-, two- or three-dimensional array of 3D points with a defined neighbourhood relation

Note 1 to entry: Each 3D point has two neighbours along each matrix dimension. The data matrix contains point

coordinates in the view coordinate system.

Note 2 to entry: The index in the data matrix is described by the symbols u, v, and w.

Note 3 to entry: The array dimensions of the data matrix should not be confused with the spatial dimensions of

the global coordinate system or view coordinate system.
© ISO 2017 – All rights reserved 3
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
4 Requirements
4.1 Units

All coordinates shall be specified in metres. Other units shall not be used. SI Prefixes shall not be used.

4.2 Recommended offset value

The offset should be set to a value so that the stored point cloud is centred on the origin of the

coordinate system.
5 x3p file format
5.1 General

An x3p file is a zip-container for areal and profile data. It can be flexibly used for point clouds

without any topology as well as for projectable 2½D topography data and for multilayer topography

representations.
NOTE A general container format is described in Reference [5].
5.2 File name extension

The name of a file stored in x3p data format shall end with the string “.x3p”. On case sensitive file

systems the string shall be typed in lower case letters.
EXAMPLE 1 samplefile.x3p
EXAMPLE 2 longer_filename example123.x3p
5.3 Minimum contents of zip-container

The zip-container representing an x3p file shall contain as a minimum the files “main.xml” and

“md5checksum.hex” in its root directory as displayed in Figure 1 a).

EXAMPLE Figure 1 b) shows a more complex example of the contents of the zip-container.

a) example with minimum contents b) example with binary encoded coordinates

of an x3p file container, text only format “bindata.bin” and binary validity mask “valid.bin”

Figure 1 — x3p container examples
5.4 Optional contents of zip-container
5.4.1 General

The zip-container may contain more files depending on the type and encoding of the stored data.

4 © ISO 2017 – All rights reserved
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
5.4.2 Binary encoded coordinates

When storing coordinates in a binary encoded file, it should be placed in a subdirectory named

“bindata” and the file should be named “bindata.bin”.

NOTE Specifying a different name does not result in a dysfunctional file, because the relative path name to

this file is stored in main.xml.
5.4.3 Validity mask

When storing a validity mask in a binary encoded file, it should be placed in a subdirectory named

“bindata” and the file should be named “valid.bin”.

NOTE Specifying a different name does not result in a dysfunctional file, because the relative path name to

this file is stored in main.xml.
5.4.4 Vendor specific extensions

Vendor specific extensions shall be used to extend x3p-format to a custom file format. Vendor specific

extensions can use any file type and any filename except the filenames defined in 5.3.

EXAMPLE A vendor specific extension could be an image file named “photography_of_sample.jpg”.

5.5 Contents and format of main.xml
5.5.1 General

The exact specification of the xml data structures used in main.xml is defined in Annex A. Here, only

the content of the elements and their usage are described.
5.5.2 Main records

The file main.xml contains a sequence of four main records and a vendor specific extension:

— Record1: header, data types and axes definitions (see 5.5.3)
— Record2: optional record containing the document’s meta data (see 5.5.4)
— Record3: the data (see 5.5.5)
— Record4: an md5 checksum of the XML-document (see 5.5.6)
— Vendor specific extensions (see 5.5.7)
5.5.3 Record1: Header, data types, and axes definitions
5.5.3.1 Revision
The Revision record shall contain the string “ISO 5436:2000”.
NOTE This is not a reference to ISO 5436, it is only an identification string.
5.5.3.2 FeatureType
5.5.3.2.1 General

The FeatureType element specifies the class of 3D data stored in the file. The contents of feature type

shall be one of the strings “PRF”, “SUR”, “PCL”. These names correspond to profile, surface and point

cloud feature types.
© ISO 2017 – All rights reserved 5
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
5.5.3.2.2 PRF – Profile

The 3D data in the x3p file represent a profile i.e. a linear sequence of 3D coordinates. Points are stored

in a one-dimensional array for single layer profiles or in a two-dimensional array for multilayer profiles.

Each point has up to two neighbours for a single layer profile or up to four neighbours in a multilayer

profile. See Figure 2.

It shall be assured that the neighbourhood relation of all points in 3D space is the same as in the array.

NOTE 1 A 3D points matrix index u, v, w should not be confused with its 3D coordinates x, y, z.

NOTE 2 The case of a two dimensional matrix is used for multilayer profile representations. The array index w

represents the index of the layer in this case.

NOTE 3 The 3D coordinates of all points in a profile do not need to be located on a straight line in 3D space.

Profile can follow any path in space.
Key
Z 3D coordinates of point at matrix location
NOTE Each point has up to two direct neighbours.
Figure 2 — Sample neighbourhood relation of a 3D point in a “PRF” type feature
5.5.3.2.3 SUR – Surface

The 3D data in the x3p file represent the topography of a projectable surface with a well-defined

topology, i.e. a neighbourhood relation for each 3D point. Points are stored in a two- or three-

dimensional array and each array element has a maximum of four or six direct neighbouring elements

respectively, see Figure 3.

It shall be assured that the neighbourhood relation of all points in 3D space is the same as in the array.

NOTE 1 A 3D points matrix position u, v, w should not be confused with its 3D coordinates x, y, z.

NOTE 2 The case of a three-dimensional matrix is used for multilayer surface representations. The array

index w represents the index of the layer in this case.
Key
Z 3D coordinates of point at matrix location u, v
u,v
NOTE Each point has up to four direct neighbours.
Figure 3 — Sample neighbourhood relation of a 3D point for a “SUR” type feature
6 © ISO 2017 – All rights reserved
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SIST EN ISO 25178-72:2017
ISO 25178-72:2017(E)
5.5.3.2.4 PCL – Point cloud

The 3D data in the x3p file represent a cloud of non-related points in 3D space. Points are stored in an

unordered list and their neighbourhood relation is unknown.

NOTE The point cloud representation may be useful for 3D data from coordinate measurement machines

(CMM) or for data from unknown sensor types with an unknown point topology.
5.5.3.3 Axes
5.5.3.3.1 General

The Axes elements shall be used to store the description of the coordinate system. It shall contain a

description for each axis in its three elements named CX, CY, and CZ of type AxisType. The structure

of AxisType elements is described in the following clauses.
5.5.3.3.2 AxisType
5.5.3.3.2.1 General

The AxisType element shall be one of the letters “I” for incremental axis or “A” for absolute axis.

5.5.3.3.2.2 Incremental axis type

For x and y axes, an incremental type defines the calculation of x and y coordinates from the matrix

indices u and v where
x, y are the spatial coordinates of the point;
u, v are the matrix indices of the point;
O is the offset of the point from the coordinate origin in metres;
I is the increment in metres.
The z axis shall not be incremental.
5.5.3.3.2.3 Absolute axis type
An absolute ax
...

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