Web Map Service (WMS)

A standard protocol developed by the Open Geospatial Consortium (OGC) for serving static map images over the Internet.

The Open Geospatial Consortium's (OGC) Web Map Service (WMS) is a standard protocol for serving georeferenced map images over the Internet. These images are generated by a map server using data from a database which is inputted via GIS data. The images are typically produced in formats such as JPEG, PNG, and GIF.

WMS provides a simple HTTP interface for requesting geospatial images from one or multiple distributed geospatial databases. A WMS server uses a HTTP interface to respond to data requests from users. Depending on the parameters of the request, these responses can be visual overlays on a map or raw geographical data. The WMS service specifies a set of operation methods which define how the requests and responses should be formed.

The primary strength of WMS is its ability to create spatially referenced visualizations dynamically from geographic information. This allows the client to request custom maps from a server, which can include multiple layers from various sources, all integrated into a single map image. It also provides options to specify the style of the final map, making it suitable for a wide range of applications, such as environmental monitoring, navigation, real estate, urban planning and more.

On the other hand, WMS only provides data as raster imagery, and does not support transmitting the attribute or vector data linked to these images. Consequently, while WMS can be used to produce a visual representation of data, it does not provide the functionality to manipulate or analyze the underlying data. To drill down into the data details, an alternative solution like the Web Feature Service (WFS) or the Web Coverage Service (WCS) might be necessary.

In the context of user requests, WMS provides three types of operations that can be performed, which include: GetCapabilities, GetMap, and GetFeatureInfo. The GetCapabilities operation allows a client to request and receive service metadata from a server. The GetMap operation retrieves a map image with specified geographic and layer parameters. The GetFeatureInfo operation retrieves information about a particular feature shown on a map.

The WMS specification provides several criteria for the input of map requests. Key parameters include BBOX (the geographic area to be shown), LAYERS (the layers to be included in the map), and STYLES (the style to be used for each layer). Other parameters can be used to further customize the request.

It is crucial to understand that the role of WMS is primarily one of visualization and presentation, making geospatial information accessible and readily understood by users, rather than providing functionality for deeper analysis or manipulation of data sets.

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