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A Web Map Service (WMS) is a standard protocol for serving geo-referenced map images over the internet that are generated by a map server. The specification was developed and first published by the Open Geospatial Consortium (OGC). WMS provides a way for different organisations to share graphical maps over the internet through specially constructed URLs.
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A key concept of WMS is that of a layer representing a basic unit of geographical information that a WMS client can request as a map image from a WMS server. |
In the WMS transaction the client sends (HTTP) requests to the server which on return sends back the requested information to the client. The WMS standard defines several request types, two of which have to be supported by any WMS servers:
- GetCapabilities: the server sends back information about the WMS meta-data and the available map layers (typically in XML format).
- GetMa: based on the specified parameters in the request (e.g. bounding box, geographic coordinate reference system, image size and format etc.), the server returns a map image for a selected layer that can be now visualised by the client.
The Metview WMS client can perform both of this these request types enabling users to perform the following actions:
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For further information on WMS standards please turn to the official documents available at the OGC web site:
http://www.opengeospatial.org/standards
Getting started
In this exercise we will build a WMS GetMap request for a Sea Surface Temperature layer from the NASA Earth Observations WMS server and visualise the resulting image in Metview.
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