Lott, Roger (International Association of Oil & Gas Producers (IOGP)) - Co-Chair,
Ryden, Keith (Esri) - Co-Chair
The initial scope of the OGC CRS Standards Working Group was to revise Abstract Specification Topic 2 - Referencing by Coordinates to the state of an adopted OGC standard and an identical ISO International Standard. The resulting Standard was approved by the OGC Technical Committee in December 2018.
Additional work items have been identified for this SWG since completion of OGC Abstract Specification Topic 2. This updated charter brings those work items into the scope of the CRS Standards
To support encoding of point motion operations described in Topic 2, a standard for coordinate deformation modelling is required. This and other coordinate operations will benefit from a single, standard, grid file format for geodetic data. This offers the following advantages:
- Grid producers do not have to create file formats themselves, provide their own software to read and interpolate their gridded data or concern themselves with lack of take-up of their data due to its proprietary distribution format.
- Survey and geographic information software vendors need to read only one grid file format, eliminating the need to repeatedly write programs to import different grids.
- End users can use a new grid file as soon as it became available, without having to wait for their application vendor to produce a software upgrade.
The new SWG work item is to define and support an encoding of the self-contained and compact description of Coordinate Reference Systems and Coordinate Operations through a simple JSON schema. The draft standard delivered will be consistent with OGC Abstract Specification Topic 2 and ISO 19111. This offers the following advantages:
- Provides a JSON encoding of coordinate reference systems descriptions for use where JSON may be considered a more natural data schema than Well Known Text.
- Ensures that a JSON schema is available that will be kept in alignment with OGC Abstract Specification Topic 2 and ISO 19111.
- Recognizing the PROJ6 origins of the PROJJSON schema contribution being used as the starting point of this work, effort will be made to try to avoid compatibility issues and to clearly document any issues identified or object names that deviate from the original OGC Abstract Specification Topic 2 and ISO 19111. If an unresolvable conflict is identified, OGC Abstract Specification Topic 2 and ISO 19111 will guide the resolution and such an issue will be clearly documented.
Additional work items are described in Description of Deliverables.
3.1 Statement of relationship of planned work to the current OGC standards baseline
This work compliments OGC Abstract Specification Topic 2, Spatial Referencing by Coordinates.
3.2 What is Out of Scope?
The CRS SWG will not consider issues associated with spatial referencing using Discrete Global Grid Systems (DGGS)
3.3 Specific Contribution of Existing Work as a Starting Point
ISO 19111:2019 and OGC Abstract Specification Topic 2
ISO 19162:2019 and OGC CRS WKT specification document
Work of the OGC CRS DWG Gridded Geodetic Data Exchange Format (GGXF) project team
Work of the OGC CRS DWG Deformation Functional Model (DFM) project team
Work of the PROJ Open Source Project to develop PROJJSON
Maintenance of OGC Abstract Specification Topic 2.
Maintenance of CRS WKT specification (18-010r7).
Specification of a standard exchange format for gridded geodetic data (GGXF).
Documentation of a standard model for deforming coordinate reference systems.
Specification of a JSON encoding for the self-contained and compact description of Coordinate Reference Systems and Coordinate Operations described in OGC Abstract Specification Topic 2 and ISO 19111