--- title: ISO 19111 — Referencing by coordinates description: Assesses ISO 19111:2019 through the adopted OGC 18-005r5 corrigendum and identifies LongitudeOne coordinate-reference limitations. canonical_html: ./iso-19111.html canonical_markdown: ./iso-19111.md --- [View HTML version](./iso-19111.html) ISO 19111 describes coordinate reference systems and coordinate operations. LongitudeOne stores reference identifiers alongside coordinates; that capability does not implement the complete CRS model or establish ISO conformance. ## Normative source - ISO, **ISO 19111:2019**, *Geographic information — Referencing by coordinates*, edition 3, January 2019: [ISO catalogue][iso2019]. - **Adopted technical reference:** OGC **18-005r5**, *OGC Abstract Specification Topic 2: Referencing by coordinates Corrigendum*, version **5.0.1**, approved **2021-03-26**, published **2021-07-02**: [official HTML][ogc2019]. Alexandre selected this reference during correction of [Story #61's review][review]. All technical citations below refer to its numbered HTML clauses; the HTML publication has no printed page numbering. **Corrigendum scope:** the preface states consistency with ISO 19111:2019 and incorporation of three editorial corrections from **ISO 19111:2019/Amd 1:2021**. The revision history identifies definition 3.18 (numbered 3.1.18 in the body), 7.4 Figure 5 and Table 2 as corrected locations. This reference uses that corrected text rather than the superseded OGC 08-015r2/2007 analysis. Separately, **OGC 20-040r3, clause 3**, explicitly identifies OGC 18-005r5 and ISO 19111:2019 as [identical in normative content][equivalence]. These are OGC's source statements, not a claim of direct inspection of the ISO publication. Later OGC revisions and additional ISO corrections are outside this assessment. ## Purpose and scope The relevant subjects are the definition of a CRS, its axes and units, identification of reference objects, and operations that change coordinates. These distinguish an identifier attached to a geometry from a complete reference system definition and from a calculation that changes its coordinates. This assessment covers the adopted 2019 model, including static and dynamic CRS metadata. CRS encodings and DBMS axis conventions remain outside this page. ## Relevant requirements **Normative summaries from OGC 18-005r5:** - **CRS definition (9.1.1):** a CRS normally combines a coordinate system with a datum or datum ensemble; a derived CRS adds a defining conversion. - **Axes and tuples (7.2, 10.1):** the coordinate system defines axis names, units, directions and sequence. A coordinate tuple has one ordinate per axis and follows that axis sequence. - **Identification (7.2):** a CRS may be identified by a full description or a register citation plus the identifier of its defining record. - **Coordinate metadata (7.3.1–7.3.2, Requirements 1–2):** all tuples in a set must share one CRS; a dynamic CRS additionally requires one coordinate epoch. - **Operations (3.1.6, 3.1.12, 12.1):** conversion changes coordinates between CRSs based on the same datum; transformation uses CRSs based on different datums. Point motion changes coordinates between epochs within one CRS. - **Conformance (4, Table 1):** separate conformance classes assess coordinate metadata, CRS descriptions and coordinate-operation descriptions. **Informative explanation:** recording `EPSG:4326` supplies a reference to a definition. It does not itself provide axes, units, datum parameters or a coordinate operation implementation. A PHP XY/XYZ/XYM/XYZM layout alone cannot establish conformity with the axes of a particular CRS. ## LongitudeOne support **Assessed implementation:** Spatial Types pre-1.0 development snapshot after `0.0.1-alpha.4`, revision `ceaee5d142c77fc3922ab50c762fa6648fea0e30`. This is evidence about a development snapshot, not a released 1.x promise. No DBMS integration is assessed. | Feature | Implementation scope | Status | Limitations | Implementation decision | Extensions | Evidence | | --------------------------- | -------------------- | ------------------- | -------------------------------------------- | -------------------------------- | --------------- | ---------------------------- | | Reference identification | Types snapshot | Partially supported | Identifier only; no full CRS definition | Integer and optional authority | None documented | [Reference value][reference] | | CRS definition | Types snapshot | Unsupported | No datum, axes or units model | Reference identity only | None documented | [Reference value][reference] | | CRS axis validation | Types snapshot | Unsupported | No CRS lookup or tuple/axis verification | Stored ordinates retained | None documented | [SRS guide][guide] | | Dynamic coordinate metadata | Types snapshot | Unsupported | No coordinate epoch or reference-frame model | Identifier metadata only | None documented | [Reference value][reference] | | Coordinate operations | Types snapshot | Unsupported | External calculation required | Relabeling preserves coordinates | None documented | [SRS guide][guide] | **LongitudeOne implementation decisions:** `SpatialReference` compares the integer identifier and optional authority. Identifier `0` is an unnamed reference rather than a wildcard. Aggregate members must share the parent's full reference. These identity rules are project behavior. Full identity matching supports a single-reference invariant, but does not establish CRS-definition or dynamic coordinate-metadata conformance under clauses 4 and 7.3. `withSpatialReference()` changes the declared reference on an immutable copy without calculating new ordinates. It therefore does not perform the coordinate operations described in OGC 18-005r5, clause 12.1. A caller must obtain the target ordinates through an external component. **Extensions:** none are documented for this assessed subset. This is not an ecosystem-wide absence claim. No blanket ISO 19111 conformance is claimed. ## Related references - [SQL/MM Spatial reference](iso-iec-13249-3.md) - [Spatial Core primitives](../../spatial-core/v1/geometry/index.md) - [Reference authoring contract](../../shared/spatial-reference-documentation-architecture.md) - [Task #66](https://github.com/longitude-one/spatial-docs/issues/66) [iso2019]: https://www.iso.org/standard/74039.html [ogc2019]: https://docs.ogc.org/as/18-005r5/18-005r5.html [equivalence]: https://docs.ogc.org/as/20-040r3/20-040r3.html#toc10 [review]: https://github.com/longitude-one/spatial-docs/pull/94#issuecomment-6109813244 [reference]: https://github.com/longitude-one/spatial-types/blob/ceaee5d142c77fc3922ab50c762fa6648fea0e30/lib/Reference/SpatialReference.php [guide]: https://github.com/longitude-one/spatial-types/blob/ceaee5d142c77fc3922ab50c762fa6648fea0e30/docs/spatial-reference-systems.md