Web Coverage Service

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 XML-based GML furnishes the default payload-encoding for transporting the geographic features, but other formats like shapefiles can also serve for transport. In early 2006, the OGC members approved the OpenGIS GML Simple Features Profile [http://portal.opengeospatial.org/files/?artifact_id=15201] .

The OGC membership defined and maintains the WCS specification. Among implementations are a [http://geoserver.org Open Source WCS] reference implementation, called GeoServer.

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.

References

* [http://www.opengeospatial.org/standards/wcs OGC Web Coverage Service]
* [https://portal.opengeospatial.org/files/?artifact_id=18153 "OpenGIS Web Coverage Service (WCS) Implementation Specification"]

External links

* [http://www.opengeospatial.org/resource/products/byspec/?specid=89 WCS implementations]