i. Abstract
The OGC Web Coverage Service (WCS) supports electronic retrieval of geospatial data as “coverages.” Coverages are digital geospatial information representing space/time-varying phenomena, specifically spatio-temporal regular and irregular grids, point clouds, and general meshes.
This document specifies the WCS core. Every implementation of a WCS shall adhere to this standard. This standard defines core requirements. Extensions to the core define extensions to meet additional requirements, such as the response encoding. Additional extensions are required in order to completely specify a WCS for implementation.
This WCS 2.1 standard extends WCS 2.0 in a backwards compatible manner by accommodating coverages as per the OGC Coverage Implementation Schema (CIS) 1.1 in addition to CIS 1.0 coverages as addressed by WCS 2.0.
ii. Keywords
The following are keywords to be used by search engines and document catalogues.
ogcdoc, OGC document, coverage, Web Coverage Service, grid, mesh
iii. Preface
This document specifies the OGC Web Coverage Service (WCS) core requirements, which are mandatory for any implementation claiming to be conformant with WCS. The WCS standard is based on the Coverage Implementation Schema (CIS), OWS Common, and OGC Abstract Topic 6. WCS 2.1 extends WCS 2.0 (which establishes how to offer coverages as per CIS 1.0) so that 2.1 servers may additionally offer coverages as per CIS 1.1. Therefore, WCS 2.1 is backwards compatible with WCS 2.0. Any service passing the WCS 2.1 conformance tests will also pass the WCS 2.0 tests. Further, all WCS 2.x extensions remain applicable in the context of WCS 2.1.
Suggested additions, changes, and comments on this draft document are welcome and encouraged. Such suggestions may be submitted by email message or by making suggested changes in an edited copy of this document
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The Open Geospatial Consortium shall not be held responsible for identifying any or all such patent rights.
Recipients of this document are requested to submit, with their comments, notification of any relevant patent claims or other intellectual property rights of which they may be aware that might be infringed by any implementation of the standard set forth in this document, and to provide supporting documentation.
iv. Security Considerations
No security considerations have been made for this standard
v. Submitting organizations
The following organizations submitted this Document to the Open Geospatial Consortium (OGC):
- Jacobs University Bremen
- rasdaman GmbH
- Envitia Ltd
- European Union Satellite Center
vi. Submitters
All questions regarding this submission should be directed to the editor or the submitters:
Name | Affiliation |
---|---|
Peter Baumann |
Jacobs University Bremen, rasdaman GmbH |
1. Scope
This document specifies how a Web Coverage Service (WCS) offers multi-dimensional (usually spatio-temporal) coverage data for access over the Internet. This document relies on and extends WCS 2.0, which operates on coverages as per the OGC Coverage Implementation Schema (CIS) 1.0, with support for coverages as per CIS 1.1.
All WCS 2.0 service extension standards remain applicable under WCS 2.1. However, in order to accommodate CIS 1.1 some extensions may need to be enhanced, leading to a minor version updates.
2. Conformance
Standardization target are WCS 2.1 implementations (currently: servers).
This document establishes a single requirements class, core, http://www.opengis.net/spec/WCS/2.1/req/core with a single pertaining conformance class, core, with URI http://www.opengis.net/spec/WCS/2.1/conf /core. Requirements and conformance test URIs defined in this document are relative paths to be appended to http://www.opengis.net/spec/WCS/2.1/.
Conformance with this standard shall be checked using all the relevant tests specified in Annex A (normative) of this document. The framework, concepts, and methodology for testing, and the criteria to be achieved to claim conformance are specified in the OGC Compliance Testing Policies and Procedures and the OGC Compliance Testing web site[1].
In order to conform to this OGC®interface standard, a software implementation shall choose to implement:
a) Any one of the conformance levels specified in Annex A (normative).
All requirements-classes and conformance-classes described in this document are owned by the standard(s) identified.
3. References
The following normative documents contain provisions that, through reference in this text, constitute provisions of this document. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. For undated references, the latest edition of the normative document referred to applies.
- OGC: OGC 07-011, Abstract Specification Topic 6: The Coverage Type and its Subtypes, version 7 (identical to ISO 19123:2005), 2007
- OGC: OGC 06-121r9, OGC Web Service Common Specification, version 2.0, 2010
· Conformance classes used: GetCapabilitiesoperation (Clause 7)
- OGC: OGC 09-146r2, OGC® Coverage Implementation Schema, version 1.0, 2012
· Conformance classes used: coverage
- OGC: OGC 09-146r6, OGC® Coverage Implementation Schema, version 1.1, 2017
· Conformance classes used: coverage
- OGC: OGC 09-110r4, OGC® Web Coverage Service – Core, version 2.0, 2012
· Conformance classes used: core
- OGC: OGC 16-083r2, Coverage Implementation Schema – ReferenceableGridCoverage Extension, version 1.0, 2017
· Conformance classes used: gmlcovrgrid
4. Terms and Definitions
This document uses the terms defined in Sub-clause 5.3 of [OGC 06-121r9], which is based on the ISO/IEC Directives, Part 2, Rules for the structure and drafting of International Standards. In particular, the word “shall” (not “must”) is the verb form used to indicate a requirement to be strictly followed to conform to this standard.
For the purposes of this document, all terms and definitions in OGC Abstract Specification Topic 6 apply.
5. Conventions
5.1 UML notation
Unified Modeling Language (UML) static structure diagrams appearing in this standard are used as described in Sub-clause 5.2 of OGC Web Service Common [OGC 06-121r9]. Further, the following conventions hold.
- UML elements having a package name of “OWS Common” are those defined in the UML model of OWS Common [OGC 06-121r9].
- UML elements having a package name of GML are those defined in the UML model of GML [OGC 07-036].
- UML elements having a package name of “SWE Common” are those defined in the UML model of SWE Common [OGC 08-094].
- UML elements having a package name of CIS are those defined in the UML model of CIS 1.0 [OGC 09-146r2].
- UML elements not qualified with a package name are those defined in this Standard.
- UML data type Any is used here as an equivalent to XML’s xsd:any.
5.2 Data dictionary tables
The UML model data dictionary is specified herein in a series of tables. The contents of the columns in these tables are described in Sub-clause 5.5 of [OGC 06-121r9]. The contents of these data dictionary tables are normative, including any table footnotes.
For the reader’s convenience, table rows describing inherited components are shaded.
5.3 Namespace prefix conventions
The following namespaces are used in this document. The prefix abbreviations used constitute conventions, but are notnormative. The namespaces to which the prefixes refer are normative, however.
Prefix | Namespace URI | Description |
---|---|---|
xsd |
XML Schema |
|
gml32 |
GML 3.2.1 |
|
gml33 |
GML 3.3 |
|
swecommon20 |
SWE Common 2.0 |
|
cis10 |
CIS 1.0 (aka GMLCOV 1.0) |
|
cis11 |
CIS 1.1 |
|
wcs20 |
WCS 2.0 |
|
gmlcovrgrid10 |
GMLCOV/CIS 1.0 |
|
wcs21 |
WCS 2.1 |
6. WCS Data Model
A WCS server offers a – possibly empty – set of coverage objects, each of which can be either a CIS 1.0 coverage or a CIS 1.1 coverage.
7. WCS Service Model
The WCS Core service model is identical to WCS 2.0, but extended with CIS 1.1 coverages in its offering (Figure 1). In particular, the requests syntax and semantics remain unchanged so that a WCS 2.1 server offers the services established in WCS Core 2.0 [OGC 09-110r4] on both CIS 1.0 [OGC 09-146r2] and CIS 1.1 [OGC 09-146r6] coverages. Syntax is added which allows differentiating between CIS 1.0 and CIS 1.1 structures as results.