用到时临时收集一下，后边有空再过来翻译。
The Web Coverage Service (WCS) supports electronic retrieval of geospatial data as
"coverages" – that is, digital geospatial information representing space-varying
phenomena.
A WCS provides access to potentially detailed and rich sets of geospatial information, in
forms that are useful for client-side rendering, multi-valued coverages, and input into
scientific models and other clients. The WCS may be compared to the OGC Web Map
Service (WMS) and the Web Feature Service (WFS); like them it allows clients to choose
portions of a server's information holdings based on spatial constraints and other criteria.
Unlike the WMS [OGC 04-024], which portrays spatial data to return static maps
(rendered as pictures by the server), the Web Coverage Service provides available data
together with their detailed descriptions; defines a rich syntax for requests against these
data; and returns data with its original semantics (instead of pictures) which may be
interpreted, extrapolated, etc. – and not just portrayed.
Unlike WFS [OGC 02-058], which returns discrete geospatial features, the Web
Coverage Service returns coverages representing space-varying phenomena that relate a
spatio-temporal domain to a (possibly multidimensional) range of properties.
The Web Coverage Service provides three operations: GetCapabilities, DescribeCoverage,
and GetCoverage. The GetCapabilities operation returns an XML document describing the
service and brief descriptions of the coverages that clients may request. Clients would
generally run the GetCapabilities operation and cache its result for use throughout a session,
or reuse it for multiple sessions. When the GetCapabilities operation does not return such
descriptions, then equivalent information must be available from a separate source, such as
an image catalog.
The DescribeCoverage operation lets clients request a full description of one or more
coverages served by a particular WCS server. The server responds with an XML document
that fully describes the identified coverages.
The GetCoverage operation is normally run after GetCapabilities and DescribeCoverage
operation responses have shown what requests are allowed and what data are available. The
GetCoverage operation returns a coverage (that is, values or properties of a set of geographic
locations), encoded in a well-known coverage format. Its syntax and semantics bear some
resemblance to the WMS GetMap and WFS GetFeature requests, but several extensions
support the retrieval of coverages rather than static maps or discrete features.