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The Open Geospatial Consortium Web Coverage Service Interface Standard (WCS) provides an interface allowing requests for geographical coverages across the web using platform-independent calls. The coverages are objects (or images) in a geographical area, whereas the WMS interface or online mapping portals like Google Maps return only an image, which end-users cannot edit or spatially analyze.
The OGC membership defined and maintains the WCS specification. Among implementations are a Open Source WCS reference implementation, called GeoServer.
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Overview
The basic Web Coverage Service allows querying and retrieval of coverages.
A WCS describes discovery, query, or data transformation operations. The client generates the request and posts it to a web feature server using HTTP. The web feature server then executes the request. The WCS specification uses HTTP as the distributed computing platform, although this is not a hard requirement.
There are two encodings defined for WCS operations:
- XML (amenable to HTTP POST/SOAP)
- Keyword-Value pairs (amenable to HTTP GET/Remote procedure call)
In the taxonomy of Web Services, WCS is best categorized as a non-RESTful RPC type service.
Data
Data may be available in several formats, such as DTED, GeoTIFF, HDF-EOS, or NITF.
Several types of data layers are supported:
- series of points, such as locations of samples
- regular grid of pixels or points, which might represent a photo
- set of segmented curves, often used for road paths
- set of Thiessen polygons, used to analyse spatially distributed data such as rainfall measurements
- triangulated irregular network(TIN), often used for terrain models
Ranges of information may be attached to locations, such as average wind speed or yield by crop type.
Software support for WCS
The Compliance and Interoperability Test Engine (CITE) is used to test reference implementations for OGC specs, including WCS. List of software that supports WCS as a client and/or server:
- GeoServer - client (read WCS) and server (serve WCS)
- gvSIG - client (read WCS)
- GDAL - client (read WCS), see details
