A Web Map Service (WMS) publishes maps via the Internet. Maps are a visual representation of geographical information, and should not be confused with the geographical data itself.
The WMS standard is being developed by the Open Geospatial Consortium (OGC) and the International Organization for Standardization (ISO).
This standard defines 3 operations:
§ GetCapabilities: gives metadata on a service level
§ GetMap: gives the map
§ GetFeatureInfo: gives information concerning specific objects on the map
These operations can be started from standard web browsers via Uniform Resource Locators (URLs). Many GIS viewers nowadays can use WMS services.
SDI-Flanders testbed WMS services:
For the time being, there are 6 WMS services offered. This list will be broadened in future. Each service contains 1 or more information layers. These layers are provided with standard colouring. In addition to this, some layers have an alternative rendering to show labels (textSymbolizer). The client can colour the information, provided he uses Styled Layer Descriptors (SLDs), according to his wishes (click here for an example (administrative boundaries are shown without colouring) and the sld). The WMS version 1.3.0 (and lower) is supported.
Below you’ll find the list with the 6 services available. The capabilities and an example map can be previewed for each service. Where relevant, you can also inquire about object information.
At the first query on this page, the user name and the web service key (not the password! - see Security below) have to be entered. This is no longer required for the next consultations during the same session.
1. Adrespos (CRAB Light) GetCapabilities, GetMap, GetFeatureInfo, Viewer
2. Grb (Large-Scale Reference Database ( ‘Grootschalig Referentie Bestand’) (GRB)) GetCapabilities, GetMap, GetFeatureInfo, Viewer
3. Gwp (Regional Plan ( ‘Gewestplan’, raster, situation 01/01/2002) GetCapabilities, GetMap, GetFeatureInfo, Viewer
4. Orthoklm (Midscale orthofoto imagery) GetCapabilities, GetMap, Viewer
5. Vha (Flemish Hydrographical Atlas (= ‘Vlaamse Hydrografische Atlas’)) GetCapabilities, GetMap, GetFeatureInfo, Viewer
6. Vrbg (Temporarily Reference Database (= ‘Voorlopig Referentiebestand’)) GetCapabilities, GetMap, GetFeatureInfo, Viewer
Security
In order to be able to use the WMS services, you need to have a user name and a web service key.
You can ask for access to the WMS services via http://login.FGIA.be/?role=cd27d5aa-6df6-4e30-8a7b-2114c370a5e5.
Your web service key can be found at the tab under “Mijn profiel”.
Security takes place via http digest authentication. If an operation is started from a standard web browser, the credentials have to be entered interactively. The most recent commercial GIS software (ex. ArcGIS 9.3) and free GIS viewers (ex. Gaia 3) allow you to specify these connection parameters and to save them in the project or context.
In self developed viewers (.NET), the credentials are attributed to the “WebRequest” or the WebClient.
Hereafter you’ll find a code example in C#.
Metadata
In the service metadata (GetCapabilities), you can find, amongst others, the following information:
§ Service information
§ Name
§ Title (descriptive name)
§ Abstract (description of the service)
§ Keyword list
§ Contact Information
§ Capability (support operations)
§ Layer information
§ Name
§ Title (descriptive name)
§ Abstract (description of the layer)
§ Projection systems (CRS [SRS in lower versions])
§ Url to the metadatabase for the respective layer (MetadataURL)
§ Colourings (Style)
§ Eventual scale restrictions (MinScaleDenominator – MaxScaleDenominator [ScaleHint in lower versions])