Geodata Discovery Service

The CGDI has developed a specification to search geospatial registries and retrieve metadata. This specification is known as the Geodata Discovery Service.

There are two profiles of the Geodata Discovery Service: stateful and stateless.

The stateful specification of the Geodata Discovery Service is based on the Z39.50 search and retrieval protocol. In Z39.50, a client can send a search query to the server, and then terminate the connection. The Z39.50 server continues to process the request, and the client may connect back to the same session to check the status of the request, or to do a secondary query within the result set that was returned from the initial search. This is unlike HTTP, where a client sends a request to a server, the server processes the request, returns the result to the client, then goes back to its initial state

A new stateless version of the Geodata Discovery Service is in development, and is intended to serve the same goals as Z39.50: to search geospatial inventory catalogues through the Internet, but without the requirement to deploy specialized Z39.50 components on the client and the server.

The draft documented specification is available from the GeoConnections Geodata Discovery Service description page.

Geodata Discovery Service in action

Fred, a forester, is using the GeoConnections Discovery Portal to find satellite imagery that he needs to calculate damage being caused by a forest fire. He discovers the Landsat-7 database by searching through the metadata description; he also uses the Geodata Discovery Service to search the inventory database through the Internet (using the Z39.50 protocol).

The results from the Geodata Discovery Service include browse images from before the fire and from after the fire started. Fred can then determine the rate and pattern of progression of the fire to try to estimate where the most effective fire-fighting effort should be concentrated.