OGC Requests

The Open Geospatial Consortium (OGC) seeks public comment on the candidate standard jointly developed by the International Organization for Standardization (ISO) and the Open Geospatial Consortium: “Geographic Information - Well-Known Text representation of coordinate reference systems” (CRS WKT).

Well-Known Text (WKT) is used as a compact machine- and human-readable representation of geometric objects and coordinate reference information, as specified two decades ago in the OGC and ISO standard “Geographic information – Simple feature access – Part 1: Common architecture.” This standard included a capability for describing coordinate reference systems as text. The original CRS WKT was subsequently extended in numerous incompatible ways, and had thus become non-interoperable.

In 2015, OGC and ISO adopted a major revision of the CRS WKT specification that allowed a rigorous description of coordinate reference systems and coordinate operations in WKT, following the data model described in OGC Abstract Specification, Topic 2, which is also published as ISO 19111:2007 - Spatial referencing by coordinates. However, OGC AS Topic 2 and ISO 19111:2007 have recently been revised. The revision of CRS WKT tracks the changes made to the CRS data model.

The new edition of the CRS WKT standard aligns with the coordinate reference system model described in ISO 19111:2018. Specifically the changes from the 2015 edition are:

• Extension to describe dynamic geodetic and dynamic vertical coordinate reference systems - coordinate reference systems in which coordinate values on the surface of the earth change with time due to tectonic deformation including a time reference (coordinate epoch) for coordinates referenced to a dynamic CRS;
• Extension to describe geoid-based vertical coordinate reference systems;
• Extension for the description of datum ensembles, groups of realizations of one terrestrial or vertical reference system that for low accuracy purposes may be merged ignoring coordinate transformation;
• A rigorous description of temporal coordinate reference systems;
• The removal (deprecation) of image coordinate reference systems; and
• The remodelling of scope and extent information.

This latest edition of CRS WKT cancels and replaces the 2015 version (also published as ISO 19162:2015), which has been technically revised. The candidate CRS WKT standard was prepared by the OGC CRS Standards Working Group and Technical Committee ISO/TC 211 Geographic information/Geomatics.

The Open Geospatial Consortium (OGC) seeks public comment on the MetOcean profile and extensions to WCS 2.1.

The Meteorological and Oceanography (MetOcean) community works with massive datacubes of content organized in 4-dimensional space and time. Extracting valuable information from these datasets requires efficient query and delivery of the content perfectly suited to the user’s needs.

The MetOcean community relies upon the OGC Web Coverage Service (WCS) to search and deliver such content. The community has developed a new profile and two new extensions to WCS 2.1 to address MetOcean requirements. The MetOcean Profile fully exploits the multi-dimensional nature of WCS2.1, which is built on the new OGC Coverage Implementation Schema (CIS) 1.1. The GetCapabilities file size is reduced by almost 2 orders of magnitude, making discovery much easier.

As the WCS2.1 core provides only general metadata, the MetOcean Profile adds community-specific metadata to this core.

Additionally, the MetOcean Profile introduces the terms “Groups” and “CoverageCollections” as a way to both efficiently access the data, and structure the return of data. The main benefit of Groups is in creating a structure that reflects the organization of the intended use of data, rather than its underlying structure. This provides a hierarchical way of nesting services. The main benefit of CoverageCollections allows for the identification of collections of data for easier access to the data.

Two extensions have also been developed to facilitate retrieval of coverage data according to the operational requirements of those using MetOcean data. One extension specifies how to extract a corridor based on a trajectory from a multidimensional coverage. The other extension defines how to extract data contained within a polygon defined either by a set of points or the radius and position of a circle point.

Through the addition of community-based metadata, Groups & CoverageCollections, and the two new operations, the efficiency of both MetOcean data access and retrieval has been increased substantially.

The Open Geospatial Consortium (OGC) seeks public comment on the latest version of the OpenSearch for Earth Observation (OpenSearch-EO) Suite of Standards.

The OpenSearch specification allows syndication of search results that can then be aggregated by one large index. It provides a simple to use description of the search interface, which is called OpenSearch Description document (OSDD). A client (e.g., a browser) can use this description to check which response formats are supported and how a query/filter can be formulated.

This OGC suite of standards specifies an Earth Observation extension to OpenSearch (OpenSearch-EO) that defines query parameters to permit the filtering of search results with fields related to Earth Observation, as well as a search response model supporting different search response encodings. This revision updates the extension primarily to include additional examples for developers. Further, two new encodings of the OpenSearch-EO conceptual model have been developed as new standards: one for encoding metadata using GeoJSON or JSON-LD and one for encoding of responses to OpenSearch-EO queries in GeoJSON or JSON-LD. These standards further integrate with the OGC Standards Baseline in that the GeoJSON responses are provided as OWS Context documents.

OpenSearch-EO specifies a series of parameters that can be used to constrain search results. In short, provision is made to filter results by sensor information, acquisition, processing parameters and other information.

This specification is complementary to the OpenSearch Geo and Time Extensions (OGC 10-032 [RD.3]) and recommends its use for spatial and temporal queries especially for EO collection and EO product metadata. Further, it defines a default response encoding based on Atom 1.0/XML [RD.22].

The Open Geospatial Consortium (OGC) seeks public comment on Part 1 of the Features and Geometry candidate standard.

The Features and Geometries candidate standard provides the requirements for defining and representing geographic features in geographic information systems, applications, databases, and data formats. This standard is being developed in multiple parts in conjunction with ISO / TC 211 and will impact or replace ISO 19107, ISO 19109, and ISO 19125. The major advantage to the approach taken with the multi-part Feature and Geometries standard is that the parts are each relatively small and focused in content and ease the burden of implementation of the standard.

The Implementation Standard Geographic information — Features and geometry – Part 1: Feature models describes how geographic information held in datasets and databases using a ‘feature model’ are structured, created, stored, queried, and manipulated.

Part 1: Feature models updates the General Feature Model with various representations, as well as how it determines the basic form of geographic information. This is derived from and extends ISO 19109, which, in its current form, only addresses schema-based data storage defined in UML, but leaves possibilities open for other non-schematic design systems.

The data structures described in the candidate standard have been made more flexible than in earlier versions of this and supporting standards. The Features and Geometry standard describes semantically-structured data sets aimed to represent reality, not the specific needs of a single application. This shifts the support of interoperability from creating transfer formats, to creating inclusive, flexible - and thereby interoperable - data stores that are usable by a wide range of applications.

Further parts will describe the distinction between planar and geodetic/ellipsoidal geometry, simple geometries, other geometry, and topology structures, while a set of parallel standards will define WKT (well-known text) and JSON (JavaScript Object Notation) for both features and geometry.