Introduction The OGC Web Coverage Service (WCS) –Coverage Collection Extension defines an extension to the WCS Core [OGC 09-110r] to the collection and description of coverage collections during processing of a new DescribeCoverageCollection request. Note As such, this CoverageCollection Extension has impact on the operational behaviour and in particular the response to a GetCapabilities response. The concept of “feature collections” is well established so given that a “coverage” is a type of feature then the extension for is easy to understand. Each “” will have an identifier that will be exposed in the “GetCapabilities” response document. Support for coverage collections are reported by the service in its GetCapabilities response.
Blue: CoverageCollection Coverage ollection overview (non-normative) It is not uncommon for a WCS server to expose many hundreds, if not thousands, of coverages. For example: A satellite instrument may provide many individual images, each a coverage, that may be composed into a single mosaic. The execution of a numerical weather prediction model may produce data for many physical quantities. Furthermore, operational meteorologists often work with the results of numerical weather prediction models as a set of 2-dimensional ‘fields’ (one for each physical quantity at each time-step and vertical level) rather than more complex 4-dimensional datasets. The resulting dataset can easily number in the thousands. A Coverageollection is a useful mechanism for grouping together coverages into a collection. The pattern is similar to a feature collection. Each Coverageis a single, uniquely identified resource specifying the member coverages. Furthermore, each member coverage within a Coverage similar characteristics such as provenance Use of Coverageresources means that it becomes simpler to refer to an aggregate set of coverage resources (e.g. using the identifier) and that common metadata can be attributed to the Coverageresource itself. A Coverageresource may contain other Coverageresources- thus enabling coverages to be grouped in arbitrarily nested sets. Where a WCS server is able to suppress information about individual coverages in its getCapabilities response, the XML document provided by the WCS end-point may be significantly smaller and easier to parse- thus mitigating challenges arising from working with very large XML documents. In such situations, a client application may gather information the Coverageresources from a WCS server, and then subsequently request information about the member coverages of a given Coverage- a subset of the complete set of coverages available from that WCS
Name Definition Data type Multiplicity Identifier of a CoverageCollection offered by this service NCName one (mandatory) metadata Reference to more metadata about this CoverageCollection OWS Common::Metadata zero or one (optional) SubCollection contained within this Coverageresource. zero or one (optional)
HTTP/GET using KVP request structure The request for HTTP/GET KVP is defined below: Table request URL encoding Name Definition Data type Multiplicity service Service identifier String, fixed to “WCS” one (mandatory) WCS service version indicator String one (mandatory)
Test method Inspect that the GetCapabilities response contains element within the element. Test type Conformance /response-extension-identification Requirement Test purpose Test method Inspect that the GetCapabilities response contains the URI within the profile element. Test type Conformance /response-coverageollectionummary Requirement Test purpose Test method Inspect the GetCapabilities response and pass if the response containing a CoverageollectionSummary elements conform. Test type Conformance