Web Mapping Services in Geomatics

Agencies such the OpenGIS Consortium (OGC) and the Canadian Geospatial Data Infrastructure (CGDI) are actively pursuing new specifications for the use of geographic-centric web services. To date, there are several published specifications that allow geospatial data providers and users of geographic information new levels of interoperability.

The benefits of these services are enormous. Here are just a few:

• Data providers can publish their data using accepted web service specifications (open source specification)
• Users can "consume" the geographic web service any not worry about proprietary file formats. More and more geographic mapping packages are adding functionality to read OGC mapping specifications.
• By using Internet Mapping software (such as Nova Scotia Maps), users can add different geographic web services from all over the world and overlay data in a single map.

Here are some of the more popular geographic web services / specifications (from the GeoConnections Internet site)

Web Map Service (WMS)

A Web Map Service can:

• Produce a map (as a picture, as a series of graphical elements, or as a packaged set of geographic feature data);
• Answer basic queries about the content of the map; and
• Tell a client what maps it can produce and which of those can be queried further.

Styled Layer Descriptor (SLD)

A Styled Layer Descriptor can enhance cartographic display, and also could allow users to specify custom styles (such as colours and symbols that a Web Map Service will use to render a map layer.

Web Feature Service (WFS)

A Web Feature Service allows a client to perform data manipulation operations on a set of geographic features. Data manipulation operations include the ability to:

• Get or Query features based on spatial and non-spatial constraints.
• Create a new feature
• Delete a feature
• Update a feature

Geographic Markup Language (GML)

GML provides a means of encoding spatial information for both data transport and storage. It is an XML (eXtended Markup Language) coding for geographic features.

GeoData Discovery Service

A Geodata Discovery Service provides a mechanism to:

• Search Metadata for Geodata; and retrieve detailed information (metadata) that describes a geodata resource, in order to evaluate its suitability to meet a need.

For additional information on open specifications in geomatics, please visit these important Internet Sites:

Open GIS Consortium
GeoConnections