Overview
ISO 19162:2019/Amd 1:2023 is Amendment 1 to ISO 19162 (Well‑known text representation of coordinate reference systems, WKT). Published by ISO in collaboration with the Open Geospatial Consortium (OGC), this amendment updates WKT syntax, definitions and semantics used to describe coordinate reference systems (CRS) in geospatial data. It clarifies dynamic/static CRS handling, datum ensembles, axis ranges, defining transformations and related tokens used in WKT.
Key topics and technical changes
- Updated definitions: New or revised definitions such as datum ensemble, geodetic coordinate reference system, and spherical coordinate system to align with ISO 19111 amendments.
- WKT grammar and tokens: Additions and edits to permitted characters, inclusion of the @ (at sign) token, and a refreshed set of allowed Latin text characters for WKT strings.
- Axis metadata and constraints:
- Mandatory declaration of axis unit (and conversion factor rules) for spatial axes.
- New optional attributes AXISMINVALUE, AXISMAXVALUE and RANGEMEANING to express axis minimum/maximum and whether wrap‑around (e.g., longitudes modulo 360°) applies.
- Dynamic frames and epochs:
- Support for dynamic reference frames and explicit datum anchor epoch (ANCHOREPOCH) to indicate epochs associated with derived frames.
- Defining transformation:
- A new DEFININGTRANSFORMATION element to reference transformations that define or relate CRSs; amendment clarifies that full transformation descriptions should not be embedded directly in a geodetic CRS WKT.
- CRS and CS rules: Table updates on permitted coordinate system (CS) types and dimensions per CRS type (geodetic, geographic, projected, vertical, temporal, engineering, etc.), including explicit support for 2D or 3D spherical coordinate systems.
- Practical examples: New and revised WKT examples (GEODCRS, PROJCRS) illustrating dynamic frames, 3D projected CRS, axis order, and axis range constraints.
- Registry link and references: EPSG registry URL updated to https://epsg.org; references aligned with ISO/TC 211 and ISO 19111 amendments.
Applications and users
This amendment is essential for:
- GIS software developers and geospatial libraries implementing or parsing WKT CRS definitions.
- National mapping and surveying agencies managing geodetic datums, epoched reference frames and transformations.
- Data integrators, database administrators and cartographers who need consistent CRS metadata for merging, transforming and validating geospatial datasets.
- Standards bodies and tool vendors ensuring interoperability with EPSG registries and OGC/ISO profiles.
Related standards
- ISO 19162 (base standard)
- ISO 19111 (Reference for spatial referencing by coordinates) - amended references incorporated into this document
- OGC specifications (interoperability and WKT usage)
Keywords: ISO 19162, WKT, coordinate reference systems, CRS, datum ensemble, axis range, defining transformation, datum anchor epoch, geodetic, EPSG, geospatial standards.