Features and Geometries JSON SWG

Chair(s):

Vretanos, Panagiotis (Peter) A. (CubeWerx)
Portele, Clemens (interactive instruments GmbH)
Harrison, Jeff (US Army Geospatial Center)
Wiersma, Gabriella (Geonovum)

Group Charter:

Download Charter document

Group Description:

1. Purpose of the Standards Working Group

The OGC Features and Geometries JSON SWG is chartered to develop a JSON encoding for geospatial feature data. This encoding is intended to build upon the foundational OGC standards (such as Simple Features), be inclusive of other geospatial JSON encodings (such as GeoJSON [1]), and support content delivery per the OGC API suite of standards. More specifically, OGC Features and Geometries JSON will build on the widely used GeoJSON standard and extend it with minimal extensions to support additional concepts that are important for the wider geospatial community and the OGC API standards.

2. Business Value Proposition

JSON as an encoding format for geospatial data is becoming increasingly popular over XML. The light weight, simple syntax, and clear human and machine readability of JSON appeals to developers. GeoJSON has become a very popular encoding, but has significant limitations that prevent broad use in more technical circumstances. At a minimum, a more-inclusive JSON encoding for geospatial feature data should:

  • include the ability to use Coordinate Reference Systems (CRSs) other than WGS84,

  • support other non-Euclidean metrics, in particular ellipsoidal metrics,

  • support more geometry types, in particular solids, and

  • provide guidance on how to represent feature properties in JSON consistent with the General Feature Model, e.g., including temporal properties.

In the future OGC Features and Geometries JSON may be extended include more complex geometries such as curves with non-linear interpolation, time-variant geometry, or geometries based on multiple coordinate reference systems.

Given the popularity of GeoJSON, the SWG will ensure that OGC Features and Geometries JSON will be specified as a superset of GeoJSON so that valid GeoJSON is also valid OGC Features and Geometries JSON.

3. Scope of Work

OGC Features and Geometries JSON is intended to fulfill a known need in the geospatial and broader communities for a JSON encoding of geospatial feature content that supports capabilities not found in GeoJSON, but which are generally more simple to implement than the OGC Geography Markup Language (GML)[2]. The OGC Features and Geometries JSON SWG will consider the elements contributing to the Business Value Proposition (above) as general requirements for defining the encoding requirements. The SWG will take on the following work actions.

  • Specify requirements for OGC Features and Geometries JSON based on the identified community needs and further consultation with members and users of geospatial data, such as the addition of CRS support.

  • Use JSON Schema to specify the syntax of OGC Features and Geometries JSON.

  • OGC Features and Geometries JSON will use a core-and-extensions approach. The initial task of the SWG will be the initial version of OGC Features and Geometries JSON and will be restricted to the requirements identified in this charter. If successful, the scope may be extended with tasks to support additional capabilities.

  • Leverage profiling requirements identified by the user community or domains to structure the design of the Standard such that profiling of the Standard is done by enumerating the conformance classes required by the community or domain.

  • Assess relevance of JSON-LD[3] to the structure of OGC Features and Geometries JSON.

  • Use Sprints and/or Hackathons to help advance the work with realistic testing of the candidate Standard against community requirements.

  • Register one or more media types for OGC Features and Geometries JSON with the OGC naming authority.

  • Develop and move the candidate Standard through the approval process.

3.1. Statement of relationship of planned work to the current OGC standards baseline

OGC Features and Geometries JSON will build upon existing OGC Standards and offer capabilities fulfilled in part (or in total) by other standards. The primary difference between this effort and other OGC standards is that OGC Features and Geometries JSON will provide a fundamental, yet flexible, encoding of geographic feature data in JSON.

  • Simple Features[4],[5]: Simple Features provides a distinct set of geometric objects for describing geospatial feature data. Simple Feaures also defines the geometry model for most other OGC feature encodings.

  • GML[2]: GML is a comprehensive encoding of features, geometry and topology in XML. GML is quite heavy for simple feature data exchange and specifies an XML encoding for many other geospatial resources that are out-of-scope of this SWG such as coverage data or coordinate reference systems.

  • GeoPackage[6]: GeoPackage defines a container for geospatial data, including feature content. GeoPackage uses SQLite as a storage mechanism.

  • KML[7]: KML is an XML encoding of geographic features focused on its visualization including the control of the user’s navigation in the sense of where to go and where to look.

  • Abstract Specification Topic 1: Features and Geometry[8]: OGC Abstract Specification Topic 1 is a comprehensive feature and geometry model from which Simple Features is derived.

  • WKT CRS[9]: The Well Known Text representation of Coordinate Reference Systems offers a standardized way to fully describe CRSs for reference by any spatial data set.

  • SensorThings API[13]: SensorThings provides an open, geospatial-enabled and unified way to interconnect the Internet of Things (IoT) devices, data, and applications over the Web. It supports GeoJSON to encode locations and features of interest.

3.2. What is Out of Scope?

OGC Features and Geometries JSON will not consider encodings beyond JSON.

Compatibility between versions of a standard is important. Revisions of OGC Features and Geometries JSON should avoid breaking existing implementations. Any Change Request that would result in a major revision of OGC Features and Geometries JSON is out-of-scope unless a 75% majority of the SWG members support the change.

Standards are important for interoperability. At the same time, it is important that standards only state requirements that are important for a significantly large group of users. Proposals for new tasks or change requests to an existing standard must identify the user groups that will benefit from the proposal and include the commitment for two independent implementations that will generate JSON in accordance with all proposed changes and for two independent implementations that will consume that JSON.

OGC Features and Geometries JSON is a modular standard. Developing profiles of OGC Features and Geometries JSON as separate standards should not be necessary and is, therefore, out-of-scope for the SWG. If a community has a need to develop a profile, the profile should be specified and governed by that community.

3.3. Specific Existing Work Used as Starting Point

OGC Features and Geometries JSON will consider GeoJSON as a starting point for a content model and extend the model based on the benefits known from implementations of the Standards from the OGC Standards Baseline referenced above as well as other specifications used for geospatial data encoding and exchange.

The UGAS-2020 Pilot[10] has developed a proposal for a "Features Core Profile", and also developed a JSON Schema encoding rule that supports GeoJSON.

 
 

4. Description of deliverables

4.1. Initial Deliverables

The following deliverables will be the initial results of work of the SWG.

  • OGC Features and Geometries JSON Standard.

  • Associated implementation guidance for OGC Features and Geometries JSON.

  • Any sample code, evidence of implementation, and/or compliance tests that might be developed in parallel to the Standard.

The targeted start date for this SWG is the first quarter of 2021, once the charter is approved. The SWG will aim to deliver an initial release of the candidate Standard for review by the end of 2021.

4.2. Additional SWG Tasks

No specific additional tasks are currently planned for the SWG, although extension to the Standard may be considered in the future.

5. Domain Working Group Endorsement

This draft charter will be presented to the Architecture DWG with a request for endorsement.

6. Other informative information about the work of this SWG

6.1. Collaboration

All work in the Standards Working Group will be public and the SWG solicits contributions and feedback from OGC members and non-OGC members to the extent that is supported by the OGC Technical Committee Policies and Procedures.

The OGC Features and Geometries JSON SWG will collaborate on Standard development using a public GitHub repository and a Gitter channel. Development of the Standard will include the use of Issues and other project tools in GitHub.

6.2. Similar or Applicable Standards Work (OGC and Elsewhere)

GeoJSON is clearly related to this work and is planned to be a valid profile of the resulting OGC Standard.

GeoJSON-T [11] extends GeoJSON by adding a "when" foreign member, either at the level of Feature or for individual geometries within a GeometryCollection.

Linked Places format [12] is GeoJSON and JSON-LD compatible. It also supports "when" elements, not only at Feature level and in geometries, but within a set of recognized properties ("names", "types", "relations"). This permits the temporal scoping of those attributes of places.

 
 

References

  • [1] IETF: IETF RFC 7946, The GeoJSON Format, 2016

  • [2] OGC: OGC 07-036r1, OpenGIS Geography Markup Language (GML) Encoding Standard 3.2.2, 2016

  • [3] W3C: JSON-LD A JSON-based Serialization for Linked Data, 2020

  • [4] OGC: OGC 06-103r4, OpenGIS Implementation Standard for Geographic information - Simple feature access - Part 1: Common architecture, 2011

  • [5] OGC: OGC 06-104r4, OpenGIS Implementation Standard for Geographic information - Simple feature access - Part 2: SQL option, 2010

  • [6] OGC: OGC 12-128r15, OGC GeoPackage Encoding Standard, 2018

  • [7] OGC: OGC 12-007r2, OGC KML 2.3, 2015

  • [8] OGC: OGC 17-087r13, OGC Abstract Specification Topic 1 Features and geometry – Part 1: Feature models, 2020

  • [9] OGC: OGC 18-010r7, Geographic information — Well-known text representation of coordinate reference systems, 2019

  • [10] OGC: OGC 20-012, UML-to-GML Application Schema Pilot (UGAS-2020) Engineering Report, 2020

  • [11] GeoJSON-T (https://github.com/kgeographer/geojson-t)

  • [12] Linked Places format (https://github.com/LinkedPasts/linked-places)

  • [13] OGC: OGC 15-076r6, OGC SensorThings API - Part 1: Sensing, 2016