OGC Spatio-Temporal Coverage / Datacube Standards

Note: this site can also be reached via shortcut https://myogc.org/go/coveragesDWG.

Table of Contents: Introduction About Educational Material Resources Related Standards News Conformance Testing Known Implementations WCS History

"Web developers who have not heard of OGC standards before immediately feel at home with these coverage standards" -- Stephan Siemen, ECMWF "WCS is the natural way to deliver and exploit coverage data." -- Jordi Escriu, Facilitator INSPIRE Thematic Cluster #3: Elevation, Orthoimagery, Reference systems and Geographical grids "As a WCS the data is of most value" -- Perry Peterson, Pyxis Innovation "CIS 1.1 is what I've been waiting for." -- Kathi Schleidt, INSPIRE expert

Note CIS, WCS and WCPS continue being stable, mature, maintained, and heavily used

Maintainer of this wiki is Peter Baumann (Constructor University, Large-Scale Scientific Information Systems Research Group and rasdaman GmbH), further contributors are welcome.

Introduction

Coverages - as per OGC, ISO, and INSPIRE standardization - constitute a unifying paradigm for the digital representations of space/time varying phenomena, concretely: spatio-temporal regular and irregular grids, point clouds, and general meshes. In particular, multi-dimensional datacubes fall under this category, such as 1-D sensor time series, 2-D satellite imagery, 3-D x/y/t image time series and x/y/z geoscientific models, 4-D x/y/z/t climate and ocean data sets, and more.

This data model is accompanied by a modular service model, the Web Coverage Service (WCS) suite of standards. Functionality of this Web API ranges from flexible datacube access and subsetting up to complex geo datacube analytics with the Web Coverage Processing Service (WCPS) datacube language.

While still fomat-independent, this conceptual overage model is conformance testable down to pixel level and harmonized with GML, SWE, and other OGC standards, thereby concretizing the abstract and therefore not interoperable ISO 19123 model.

About

This site is part of the Open Geospatial Consortium (OGC) and maintained by its Coverages Domain Working Group (Coverages.DWG) which uses this site for providing information about standardization of coverages.The OGC Coverages.DWG is a community oriented working group established for facilitating exchange on the OGC coverage data and service standards. The Coverages.DWG does not directly revise OGC standards, but rather enables collaboration and communication between groups with spatio-temporal modeling interests (BigData.DWG, Temporal.DWG, SensorThings, etc.).

Contact: This site is maintained by Peter Baumann ( Large-Scale Scientific Information Systems Group, Constructor University and rasdaman GmbH). He is also Coverages.SWG chair together with Jerome St-Louis (Ecere).

This Twiki as well as the corresponding email list provide information about the standards, including tutorials and the authoritative specification sources. Further, it constitutes a public forum for communication. Anyone can edit this wiki, but, of course, responsibly. Instructions can be found on the TWiki Text Formatting Rules page.

Educational Material

There is a large amount of introduction and training material available, listed from overview to detailed:

• start here: coverage data and service model: an overview article, also
• expert overview: synopsis of WCS suite and all specifications, including adopted standards and draft candidate standards
• Wikipedia articles on the OGC coverage data model Coverage Implementation Schema (CIS) and its streamlined service model, the Web Coverage Service (WCS) suite with the Web Coverage Processing Service (WCPS) geo datacube analytics language.
• A 15min primer video, deepened through the EarthServer webinar collection
• an illustration of the coverage data and service suite "big picture": Coverage data and service definition in OGC and Coverages FAQ
• live sandbox services for WCS and WCPS, embedded into a general set of 1-D through 5-D demos
• hands-on tutorials, often coming with sample data
• Several publications explain and exemplify use of WCS, as well as the technological advances made with WCS 2. Whenever writing scientific articles about coverages and WCS, do the editors a favour and cite their scientific work, following good practice - much appreciated!

Resources

• synopsis of WCS suite and all specifications, including adopted standards and draft candidate standards
• WCS standards documents official location
• Datacubes details and Coverages FAQ
• ideas for future work on coverages/GMLCOV and the WCS suite

Related Standards

• ISO TC211:
  • ISO 19123-1: Coverage Fundamentals (abstract coverage model), 19123-1 draft; status: adopted by ISO, adopted by OGC as revision of Abstract Topic 6
  • ISO 19123-2: Coverage Implementation Schema = CIS 1.0; next step: extend with CIS 1.1 General Grid Coverage
  • ISO 19123-3: Coverage Processing Fundamentals (abstract coverage processing model), 19123-3 draft; status: adopted by OGC as revision of Abstract Topic 6
• INSPIRE (legal framework for a common European SDI):
  • WCS as Download Service, based on OGC CIS, WCS-Core and WCPS; see also the officially endorsed INSPIRE-WCS Good Practice
  • INSPIRE WCS and WCPS -- seminar by Jordi Escriu, Kathi Schleidt, Peter Baumann at the 2019 INSPIRE workshop, Helsinki

News

• August 2024: OGC announces Validation Tools August 2024 Release of Beta environment, among others with an update of the WCS 2.0 test suites - thanks, Dirk Stenger & team
• June 2024: Functional enhancement to WCS proposed: interpolated slicing at slice points between grid positions
• June 2024: 19123-1 and 19123-3 have finished adoption cycle to become Abstract Topic 6, soon to be published
• September 2023: OGC adoption of 19123-1 and 19123-3 as new Abstract Topic 6 started
• June 2023: 19123-1 and 19123-3 adopted by ISO TC211 without any NO vote
• February 2023: 19123-1 and 19123-3 presented at OGC TC meeting to Coverages.SWG and Architecture.DWG
• November 2022: 19123-1 and 19123-3 out for FDIS ballot, following resolution of 19111-related comments in tight collaboration with UK
• March 2022: 19123-1 and 19123-3 successfully pass DIS ballot; UK comments about 19111 use to be resolved
• October 2021: 19123-3 (draft) submitted by the editing team for DIS ballot
• August 2021: Following a positive ballot with overwhelming support by the nations, ISO accepts 19123-3 as an NWIP to establish coverage processing fundamentals, based on the twin specification 19123-1 defining the abstract coverage model.
• June 2021: the rasdaman-based INSPIRE coverage portal, https://inspire-wcs.eu, gets endorsed as the (single) official Good Practice for INSPIRE coverages.
• November 2020: MIG-T has adopted the INSPIRE coverage portal, https://inspire-wcs.eu, as a candidate good practice. INSPIRE-WCS is based on OGC CIS, WCS and WCPS
• November 2020: Delegations had no objection to ISO WD 19123-1, so it can move on to next level, Committee Draft (CD)
• June 2020: ISO TC211 WG6 has distributed a Working Draft of 19123-1, the forthcoming abstract coverage standard complementing the concrete 19123-2 = OGC CIS.
• 2019: WCS 2.1 have been adopted, together with updates in the corresponding WCS extensions. This adds CIS 1.1 GeneralGridCoverage as a unified, simplified coverage type encompassing all raster / gridded coverage types. Further, WCPS 1.1 is established.
• July 2019: ISO adopts SQL/MDA (Multi-Dimensional Arrays) as 9075-15:2019. This Part 15 of SQL adds datacube analytics into the database language. Note that OGC WCPS is structurally equivalent to SQL/MDA (WCPS requests can be transformed automatically into SQL), however WCPS adds spatial and temporal semantics whereas MDA is domain-agnostic and can handle Earth, Space, and Life science data.
• September 2017: At the Southampton TC meeting the Coverages.DWG has moved to approve establishing a Datacube Domain Working Group; close collaboration between the Coverages.DWG and the forthcoming Datacube.DWG is planned as the OGC datacube standard is the Coverage Implementation Schema.
• April 2017: CIS 1.1 is adopted by OGC as an Interface Standard. This opens the way for introducing CIS 1.1 to ISO to become the next version of ISO 19123-2.

Conformance Testing

• WCS: conformance tests are established and available for WCS Core; GET KVP; XML/POST; SOAP; Range Subsetting; Scaling; Interpolation; Processing; still in the pipeline is CRS.
• Coverages: for GML-encoded coverages, there is a conformance tests at http://cite.opengeospatial.org/teamengine/about/gml32/3.2.1/site/ .

Known Implementations

WCS enjoys a large and growing number of implementations, such as the following:

• OGC compliance listing, such as WCS 2 Core - CAVEAT: WCS 1.x (deprecated since many years) and WCS 2.x (current, stable) are intermixed
• open-source projects: rasdaman (WCS Reference Implementation), MapServer, EOxServer, GeoServer, GDAL, QGIS, OpenLayers, OPeNDAP/Hyrax, George Mason University, NASA GSFC, openEO, ...
• commercial products: Envitia ChartLink, Pyxis WorldView Studio, Constellation-sdi, Pixia, ESRI ArcGIS, Oracle Spatial, ...

Note that the list above is not authoritative (the page maintainers do not regularly check the links) and does not constitute any endorsement nor a statement of OGC nor anybody else about conformance. Information is provided as is, without any warranty.

Know more? Let us know!

WCS History

The current version of WCS is 2.1. Functionally, it is identical to its predecessor WCS 2.0.1, but it extends the coverage types serviceable with GeneralGridCoverage as per CIS 1.1. This new coverage type unifies and simplifies grid coverages, in particular incporporating RectifiedGridCoverage and ReferenceableGridCoverage as pwe WCS 2.0.

WCS 2.0 has several significant advantages over previous versions: it relies on the GML coverage model, leading to increased interoperability as well as harmonization across OGC standards; among the main features are:

• extends beyond pure raster grids to support all coverage types which GML 3.2.1 knows, e.g., curvilinear grids, irregular grids, point clouds, surface coverages; general meshes;
• crisp and modular, consisting of a small mandatory core and a structured universe of optional extensions;
• harmonized with OGC OWS-Common, GML, SWE, WMS, WCPS, and WPS
• has a clear, formally specified syntax (XML Schema) and semantics (Schematron) easing understanding and implementation;
• testable: for the first time, pixel contents is subject to conformance testing. In other words: conformance of coverage data and services can be tested down to single pixel level.

WCS 1 is the outdated, deprecated version of WCS. It is not compatible with WCS 2, as indicated by the major version number change (cf. OGC versioning rules). WCS 1, a stepstone in the learning curve about coverages, suffered from some known issues, in particular: lack of interoperability. It had its own coverage model which has been abondoned in WCS 2 for the sake of aligning with GML coverages.

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