Overview
EN ISO 19111:2020/A2:2023 (ISO 19111:2019/Amd 2:2023) is Amendment 2 to the international standard for Geographic information - Referencing by coordinates. Prepared by ISO/TC 211 in collaboration with CEN/TC 287 and the OGC, this amendment updates definitions, UML models and class tables that specify how coordinate reference systems (CRS), coordinate systems and axes are defined and related to coordinate operations. National adoption was mandated for CEN members by February 2024.
Key topics and technical requirements
- Terminology updates: Revised definitions such as datum ensemble, geodetic coordinate reference system, and spherical coordinate system. Clarifies examples and notes (e.g., datum ensemble “WGS 84” realizations and acceptable “approximate” merging thresholds - typically under 1 decimetre but may be up to 2 metres).
- New CRS types: Adds compound CRS variations (e.g., Derived projected 2D + Vertical CRS and Derived projected 2D + Engineering 1D (near vertical)).
- Spatio‑parametric CRS: Defines compound CRSs that combine a 2D spatial CRS (geographic, projected, or engineering) with one or more parametric CRS components to form 3D CRSs.
- UML and class model changes: Replaces and extends UML diagrams (Figure 9) and class tables for GeodeticCRS, VerticalCRS, CoordinateSystem, and SphericalCS, clarifying associations (e.g., coordinate system aggregation, datum association, deformation/velocity models, and coordinate operations).
- Axis naming and constraints: Specifies permitted axis names for CRS types (Cartesian, ellipsoidal geographic, spherical, vertical) and enforces axis unit requirements.
- Coordinate operations association: Clarifies the relationship between CRS and coordinate operations, with references to class diagrams.
Practical applications and users
This amendment is essential for anyone building, integrating or validating coordinate-referenced data and services:
- National mapping agencies & surveyors: Ensure consistent CRS definitions, vertical reference frames and transformations.
- GIS software developers & spatial DBAs: Implement standards-conformant CRS classes, axis naming, and coordinate operation linkages (UML guidance).
- Geodesists & geomatics engineers: Model geodetic reference frames, datum ensembles and velocity/deformation models.
- Data integrators & spatial analysts: Merge datasets across CRS realizations safely and understand “approximate” merging thresholds.
- Standards bodies & implementers: Align national profiles with EN/ISO requirements and interoperability expectations.
Related standards
- ISO 19111 (base standard, 2019) - Referencing by coordinates
- Other ISO 191xx series standards for geographic information (geodetic reference frames, metadata, transformations) and OGC specifications for CRS encoding and services.
Keywords: ISO 19111, EN ISO 19111:2020/A2:2023, geographic information, coordinate reference system, CRS, datum ensemble, geodetic CRS, vertical CRS, spherical coordinate system, GIS standards, UML.
