ISO 19162:2019
(Main)Geographic information — Well-known text representation of coordinate reference systems
Geographic information — Well-known text representation of coordinate reference systems
This document defines the structure and content of a text string implementation of the abstract model for coordinate reference systems described in ISO 19111. The string defines frequently needed types of coordinate reference systems and coordinate operations in a self-contained form that is easily readable by machines and by humans. The essence is its simplicity; as a consequence there are some constraints upon the more open content allowed in ISO 19111. To retain simplicity in the well-known text (WKT) description of coordinate reference systems and coordinate operations, the scope of this document excludes parameter grouping and pass-through coordinate operations. The text string provides a means for humans and machines to correctly and unambiguously interpret and utilise a coordinate reference system definition with look-ups or cross references only to define coordinate operation mathematics. A WKT string is not suitable for the storage of definitions of coordinate reference systems or coordinate operations because it omits metadata about the source of the data and may omit metadata about the applicability of the information.
Information géographique — Représentation textuelle bien lisible de systèmes de référence par coordonnées
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 19162
Second edition
2019-07
Geographic information — Well-
known text representation of
coordinate reference systems
Information géographique — Représentation textuelle bien lisible de
systèmes de référence par coordonnées
Reference number
ISO 19162:2019(E)
©
ISO 2019
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ISO 19162:2019(E)
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© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO 2019 – All rights reserved
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ISO 19162:2019(E)
Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms .10
4 Conformance requirements .10
5 Backus-Naur Form notation and syntax .11
6 WKT string form .12
6.1 Overview .12
6.2 Encoding .12
6.3 Characters used in WKT .12
6.3.1 Basic characters .12
6.3.2 Numbers .13
6.3.3 Date and time .14
6.3.4 CRS WKT characters .15
6.3.5 Double quote .15
6.4 Delimiter .15
6.5 Case sensitivity .16
6.6 Reserved keywords .16
6.7 Backward compatibility .18
7 WKT representation of common attributes .18
7.1 General .18
7.2 Name .18
7.3 Scope, extent, identifier and remark .19
7.3.1 General.19
7.3.2 Usage (scope and extent) .19
7.3.3 Identifier .22
7.3.4 Remark .23
7.4 Unit and unit conversion factor .24
7.4.1 Unit description .24
7.4.2 Conversion factor — Spatial and parametric units .25
7.4.3 Conversion factor — Temporal quantities.25
7.4.4 Default unit .26
7.5 Coordinate system .26
7.5.1 Syntax .26
7.5.2 Coordinate system type, dimension and coordinate data type .29
7.5.3 Axis name and abbreviation .29
7.5.4 Axis direction .30
7.5.5 Axis order .31
7.5.6 Axis unit and coordinate system unit .32
7.5.7 Examples of WKT describing coordinate systems .33
7.6 Datum ensemble .34
7.7 Dynamic coordinate reference systems .36
8 WKT representation of geodetic and geographic coordinate reference systems .37
8.1 Overview .37
8.2 Geodetic reference frame (geodetic datum) . .38
8.2.1 Ellipsoid .38
8.2.2 Prime meridian .39
8.2.3 Geodetic reference frame (datum) .40
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ISO 19162:2019(E)
8.3 Coordinate systems for geodetic and geographic CRSs .41
8.4 Examples of WKT describing a geodetic or geographic CRS .42
9 WKT representation of projected CRSs .43
9.1 Overview .43
9.2 Base CRS .43
9.2.1 General.43
9.2.2 Ellipsoidal CS unit .44
9.3 Map projection .45
9.3.1 Introduction .45
9.3.2 Map projection name and identifier .46
9.3.3 Map projection method .46
9.3.4 Map projection parameter .47
9.4 Coordinate systems for projected CRSs .47
9.5 Examples of WKT describing a projected CRS .47
10 WKT representation of vertical CRSs .49
10.1 Overview .49
10.2 Vertical reference frame (vertical datum) .50
10.3 Vertical coordinate system .50
10.4 Example of WKT describing a vertical CRS.51
11 WKT representation of engineering CRSs .51
11.1 Overview .51
11.2 Engineering datum .51
11.3 Coordinate systems for engineering CRSs .52
11.4 Examples of WKT describing an engineering CRS .52
12 WKT representation of parametric CRSs .53
12.1 Overview .53
12.2 Parametric datum .53
12.3 Parametric coordinate system .53
12.4 Example of WKT describing a parametric CRS .53
13 WKT representation of temporal CRSs .54
13.1 Temporal CRS .54
13.2 Temporal datum .54
13.3 Temporal coordinate system.55
13.3.1 General.55
13.3.2 Axis unit for temporalDateTime coordinate systems .55
13.3.3 Axis unit for temporalCount and temporalMeasure coordinate systems .55
13.4 Examples of WKT describing a temporal CRS .55
14 WKT representation of derived CRSs .56
14.1 Overview .56
14.2 Deriving conversion .57
14.2.1 General.57
14.2.2 Derived CRS conversion method .57
14.2.3 Derived CRS conversion parameter .58
14.2.4 Derived CRS conversion parameter file .58
14.2.5 Derived CRS conversion example .59
14.3 Derived geodetic CRS and derived geographic CRS.59
14.3.1 Representation .59
14.3.2 Example of WKT describing a derived geographic CRS .61
14.4 Derived projected CRS .61
14.4.1 Representation .61
14.4.2 Example of WKT describing a derived projected CRS .62
14.5 Derived vertical CRS .63
14.6 Derived engineering CRS .63
14.7 Derived parametric CRS .64
14.8 Derived temporal CRS .64
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ISO 19162:2019(E)
15 WKT representation of compound coordinate reference systems .65
15.1 Overview .65
15.2 Examples of WKT describing a compound CRS .65
16 WKT representation of coordinate epoch and coordinate metadata .66
16.1 Coordinate epoch .66
16.2 Coordinate metadata .67
17 WKT representation of coordinate transformations and coordinate conversions
excluding map projections .68
17.1 Coordinate operations .68
17.2 Transformation and conversion components .68
17.2.1 Operation name and version .68
17.2.2 Source and target CRS .68
17.2.3 Transformation and conversion name and identifier .69
17.2.4 Coordinate operation method .69
17.2.5 Coordinate operation parameter .69
17.2.6 Coordinate operation parameter file .70
17.2.7 Interpolation CRS .70
17.2.8 Coordinate operation accuracy .70
17.2.9 Other coordinate operation attributes .71
17.3 Examples of WKT describing a coordinate transformation .71
18 WKT representation of point motion operations .72
19 WKT representation of concatenated coordinate operations.73
19.1 General .73
19.2 Examples of WKT describing a concatenated coordinate operation.75
20 WKT representation of CRS and coordinate operation couplets .76
20.1 Bound CRS .76
20.2 Bound CRS components .77
20.2.1 Abridged coordinate transformation .77
20.2.2 Coordinate operation method in abridged coordinate transformations .77
20.2.3 Abridged coordinate transformation parameter .77
20.2.4 Coordinate operation parameter file .78
20.3 Examples of WKT describing a bound CRS .78
Annex A (normative) Abstract test suite .80
Annex B (informative) Recommended practice for implementation .89
Annex C (informative) Mapping of concepts from previous versions of CRS WKT .92
Annex D (informative) Backward compatibility with ISO 19162:2015 .103
Annex E (normative) Triaxial ellipsoid .107
Annex F (informative) Identifiers for coordinate operation methods and parameters .108
Bibliography .113
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ISO 19162:2019(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 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 211, Geographic information/Geomatics in
close collaboration with the Open Geospatial Consortium (OGC).
This second edition cancels and replaces the first edition (ISO 19162:2015), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— updates to reflect the changes made in ISO 19111:2019 from its previous edition ISO 19111:2007
to describe dynamic geodetic reference frames, three-dimensional projected coordinate reference
systems, datum ensembles and coordinate metadata;
— remodelling of the descriptions of temporal coordinate reference systems, to reflect the changes
made in ISO 19111:2019;
— the correction of minor errors.
Further details are given in Annex D.
In accordance with the ISO/IEC Directives, Part 2, 2018, Rules for the structure and drafting of
International Standards, in International Standards the decimal sign is a comma on the line. However,
the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures) at its
meeting in 2003 passed unanimously the following resolution:
“The decimal marker shall be either a point on the line or a comma on the line.”
In practice, the choice between these alternatives depends on cus
...
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