WhereGroup

Web Mapping Service WMS

The best known and most commonly used OGC specification is the Web Map Service. This specification basically defines the communication syntax and parametres for a client to retrieve a map representation from a OGC WMS. The returned map is delivered e.g. in JPG or GIF format to the client, hence is not structured and does not provide any capabilities to update or create represented geometries.

The following example query dynamically retrieves the below image from the NASA JPL WMS:

Web Feature Service OGC WFS

The Web Feature Service provides geometries and attributes in a structured format, such as OGC GML, to the client. It's core strengths are to search, find and display geospatial objects, which depending on the client can also be newly created, updated and returned to the OGC WFS. Typically the requirements for cartographic maps would be addressed by one or more OGC WMS, which could be complemented by OGC WFS for geoobject handling capabilities.

Geospatial Data Format OGC GML and GeoRSS

The Geography Markup Language is a XML format for describing geospatial data.

All information on a geo-object is translated into one XML representation, which overcomes the typical split approach between storing geometry information and attributes in a separate table from each other.

OGC GML is the standard format of the Web Feature Service interface and is due to its advantages over e.g. shapefiles increasingly used as a data exchange format.

Inspired by W3C's RDF the Open Source Community developed GeoRSS, which due to its simplified nature combines the benefits of News-Feeds with georeferencing. It can be extended flexibly to include heavy lifting OGC GML helping to close the gap between rather more static spatial data and news feed.

KML and KMZ, the current formats used by Google Maps are also simmilar to OGC GML and should in future be consolidated through the OGC standardisation processes.

Web Map Context WMC

A Web Map Context document stores user specific session information for a GeoPortal application or a Desktop GIS. The document contains all information on the status of the components needed e.g. for a mapping project in a distributed GDI. Due to its standardised nature, this enables the creation of tuely interoperable outputs.

Structured Access: SFS

The Simple Features for SQL (SFS) specification defines the binary structure and methods of geospatial objects for storage in database such as PostgreSQL and PostGIS. This is one of the core building blocks for architectures to support anything from simple geospatial browsing to highly sophisticated data processing.