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OGC 01-068r3

Web Map Service Implementation Specification

1 Scope

This OpenGIS

®

Standard specifies the behavior of a service that produces georeferencedmaps. This standard specifies operations to retrieve a description of the maps offered bya service instance, to retrieve a map, and to query a server about features displayed on amap.This OpenGIS

®

Standard is applicable to pictorial renderings of maps in a graphicalformat. This standard is

not

applicable to retrieval of actual feature data or coverage datavalues.A Web Map Service produces maps of georeferenced data. We define a "map" as avisual representation of geodata; a map is not the data itself. These maps are generallyrendered in a pictorial format such as PNG, GIF or JPEG, or occasionally as vector-basedgraphical elements in Scalable Vector Graphics (SVG) or Web Computer GraphicsMetafile (WebCGM) formats. This specification standardizes the way in which maps arerequested by clients and the way that servers describe their data holdings. This documentdefines three operations, the first two of which are required of every WMS.

GetCapabilities

(required): Obtain service-level metadata, which is a machine-readable(and human-readable) description of the WMS's information content and acceptablerequest parameters.

GetMap

(required): Obtain a map image whose geospatial and dimensional parametersare well-defined.

GetFeatureInfo

(optional): Ask for information about particular features shown on amap.A standard web browser can ask a Web Map Service to perform these operations simplyby submitting requests in the form of Uniform Resource Locators (URLs) [IETF RFC2396]. The content of such URLs depends on which of the tasks is requested. All URLsinclude a specification version number and a request type parameter. In addition, wheninvoking GetMap a WMS Client can specify the information to be shown on the map(one or more "Layers"), possibly the "Styles" of those Layers, what portion of the Earth isto be mapped (a "Bounding Box"), the projected or geographic coordinate referencesystem to be used (the "Spatial Reference System," or SRS), the desired output format,the output size (Width and Height), and background transparency and color. When

OGC 01-068r3

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invoking GetFeatureInfo the