ISO 19168-2:2022

Overview - ISO 19168-2:2022 (Geospatial API for Features - CRS by Reference)

ISO 19168-2:2022 is an ISO-published extension of the OGC API - Features family that defines how a Web API advertises, references and uses Coordinate Reference Systems (CRS) by URI. Building on ISO 19168-1 (Part 1: Core), this standard describes server behaviour for presenting geometry-valued properties in one of a collection’s supported CRSs, how CRS identifiers are discovered, and how spatial queries (for example bounding boxes) can be expressed in those CRSs.

Key technical topics and requirements

• CRS by URI: Every supported CRS must be referenceable by a uniform resource identifier (URI). Recommended format model: http://www.opengis.net/def/crs/{authority}/{version}/{code} (typical authorities: EPSG, OGC).
• Discovery (collection metadata):
  • The collection object must include a crs property listing supported CRS identifiers.
  • The list must include the default CRS(ess) defined in Part 1: Core (e.g. http://www.opengis.net/def/crs/OGC/1.3/CRS84 and http://www.opengis.net/def/crs/OGC/0/CRS84h).
• Storage CRS: If features are stored in a single CRS, the collection object shall include storageCrs. If the storage CRS is dynamic (e.g. ITRF/WGS84 realizations), the recommended storageCrsCoordinateEpoch can indicate coordinate epoch.
• Query and access: Parameters such as bbox-crs and crs (used to request output coordinates or bounding boxes in a particular CRS) and related output-format considerations are defined to enable server-side response in selected CRSs.
• Conformance & testing: A conformance class and an abstract test suite (Annex A) are defined; implementers should follow OGC compliance testing policies.

Practical applications and who should use it

• Web API developers and GIS backend engineers who need to serve vector features in multiple coordinate systems.
• National mapping agencies, spatial data infrastructures (SDIs), and data providers that must expose data with explicit CRS metadata and support client-specified CRS queries.
• GIS software vendors and integrators implementing OGC/ISO-compliant feature APIs to ensure geospatial interoperability, consistent coordinate transformations, and unambiguous dataset discovery.
• QA/test teams validating API conformance to CRS handling and metadata requirements.

Related standards

• ISO 19168-1:2020 (Geospatial API for Features - Part 1: Core)
• ISO 19111 (Referencing by coordinates) - background on reference frames and coordinate epoch
• OGC API - Features specifications and EPSG/OGC CRS registries

Adopting ISO 19168-2:2022 improves clarity around CRS URIs, enables reliable server-side reprojection and bbox queries, and strengthens interoperability across web-based geospatial services.