OGC Spatio-Temporal Coverage / Datacube Standards
Table of Contents:
- "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
- "CIS 1.1 addressed many of the issues faced with CIS 1.0 and GML 3.3 coverages in a neat way." -- Ilkka Rinne, INSPIRE expert
- "The WCS 2.0 XML schema set is much easier to use than the 1.x XML; it validates and is better organized" -- OPeNDAP
Note: you can reach this site under the shortcut http://myogc.org/go/coveragesDWG .
Maintainer of this wiki is Peter Baumann ( Jacobs University Bremen
and rasdaman GmbH
s - 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.
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. See also the Temporal.DWG
which specifically addresses temporal data aspects.
The group is chaired by Peter Baumann ( Jacobs University Bremen
and rasdaman GmbH
) and Stephan Meissl ( EOX IT Services GmbH
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
Coverage Data and Service Model
If you are new to coverage world, then you may want to start with the following step-by-step introductions:
- ISO TC211:
- ISO 19123-1: Abstract coverage model. Currently being reworked from ISO 19123 = OGC Abstract Topic 6.
- ISO 19123-1: Coverage Implementation Schema = CIS 1.0; next step: extend with CIS 1.1 GeneralGridCoverage
- INSPIRE (legal framework for a common European SDI):
- 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.
- November 2015: Following successful presentation in the OAB, the new OGC Coverage Implementation Schema (CIS) 1.1 is now being rolled out for public comments.
- September 2015: New coverage model approved by WCS.SWG, now entering the adoption pipeline: Coverage Implementation Schema (CIS) 1.1 (backwards compatible extension to GMLCOV, renamed to better reflect contents) -- see CoveragesBigPicture
- August 2015: Enterprise Architect UML model of WCS suite uploaded
- August 2015: WCS-T passed RFC without change requests, now to be presented to TC prior to voting period
- March 2015: WCS-T 2.0 released for RFC. It adds insert, delete, and update capabilities to a server.
- September 2014:OGC Technical Meeting in Calgary:
- OGC approaches ISO TC211 to adopt OGC GMLCOV, WCS Core, and WCS POST/XML as ISO standards. JAG (Joint Advisory Group) was tasked to initiate the process.
- coverage encodings for JPEG200, GMLJP2 adopted; JPIP is on its way
- WCS-T adopted as DP
- January 2013:In OWS-9, WCS has been brought close to completion by establishing a series of specifications, Abstract Test Suites (ATSs) and Executable Test Scripts (ETSs):
- Specs added: WCS Processing Extension v2;
- ATSs added: Range Subsetting, Scaling, Interpolation, CRS, Processing, GeoTIFF;
- ETSs added: GMLCOV Corrigendum 1.0.1, WCS Core Corrigendum 2.0.1, CRS Extension, EO-WCS.
- October 2012: GeoTIFF and JPEG2000 format encodings for coverage have been released by the WCS.SWG, recommending them for public Request for Comment (RFC).
- August 2012: By vote of OGC, the WCS GET-KVP corrigendum version 1.0.1 has been accepted. It provides a slight modification necessary for the format encoding flexibility introduced with GMLCOV 1.0.1 and WCS 2.0.1.
- August 2012: The Range Subsetting Extension has been released by the WCS.SWG, recommending it for public Request for Comment (RFC).
- August 2012: the OGC Coordinate Reference System (CRS) Name Type Specification (NTS) [OGC 11-135] has been released by the WCS.SWG, recommending it for public Request for Comment (RFC) as a Best Practice Paper (available on this page); this document establishes a uniform naming system for CRS identifiers, allowing general multi-dimensional CRSs.
- July 2012: Corrigenda have been published for WCS Core and GML Application Schema - Coverages (GMLCOV).
- May 2012: rasdaman is the first WCS implementation to pass the WCS Core test suite and, therefore, becomes candidate reference implementation.
- December 2011:a proposal for OGC Name Type Specification for Coordinate Reference Systems (CRSs) has been presented, together with an open-source registry implementation. During the next weeks this resolver will be set up as a prototype service by OGC.
- EO-WCS (OGC® Web Coverage Service 2.0 Interface Standard - Earth Observation Application Profile, OGC 10-140) recommended for vote by WCS.SWG
- GeoTIFF Profile (OGC® GML Application Schema - Coverages - GeoTIFF Coverage Encoding Profile, OGC 12-100r1) ready by WCS.SWG
- WCS CRS Extension passed public Request for Comment, now under voting
- 4 WCS extension drafts ready by WCS.SWG, waiting for OGC's roll-out: WCS Range ("band") Subsetting Extension, WCS Scaling Extension, WCS Interpolation Extension, WCS Processing Extension
- WCS Application Profile MetOcean commenced
- WCS RESTful interface under finalization
- The CRS Name Type Specificationis adopted by OGC, and the corresponding CRS resolver is running at OGC -- from now on, spatial, temporal, and "abstract" coordinate axes can be treated alike, and can be mixed freely (such as temporal WGS84, or CRSs for x/t and y/z slices as produced by a WCS)
WCS enjoys a large and growing number of implementations, such as the following:
- OGC compliance listing (search for "wcs")
- open-source projects: rasdaman (WCS Core Reference Implementation), MapServer, EOxServer, GeoServer, GDAL, QGIS, OpenLayers, OPeNDAP/Hyrax, George Mason University, NASA GSFC, ...
- commercial products: Envitia ChartLink, Pyxis WorldView Studio, Constellation-sdi, Pixia, ESRI ArcGIS, ...
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.
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.