A Cascading WMS Case Study: Haiti

On Tuesday January 12 2010, Haiti was hit by a catastrophic earthquake of magnitude 7.0. On January 13 2010, CBS news estimated that three million people were affected by the quake; the Haitian Government reported that between 217,000 and 230,000 people have died, an estimated 300,000 injured, and an estimated 1,000,000 homeless.

Many countries responded to the appeals and launched fund-raising efforts, as well as sending search and rescue teams. By January 26, many organizations had collected sufficient geographic data about Haiti to support local emergency responses. In addition to the many on-line map services deployed for the relief effort, CubeWerx and The Carbon Project deployed a Cascading Web Map Service (WMS) as part of the growing open information network for Haiti.

The service, offered by CubeWerx as a free public resource, helped support relief efforts, rebuilding communications and supported data update operations. The practical benefit of the service is to provide a simple, single access point for any client applications like Gaia, Google Earth and others. CubeWerx WMS service is currently chaining WMS services from New York Public Library, University of Cincinnati, Calit2, Haiti.opensgi.net, CubeWerx and others, as well as imagery from GeoEye and DigitalGlobe from a variety of WMS services.

An overwhelming response

In emergency response situations, first responders need accurate information immediately. The overwhelming response of the mapping community resulted in an unprecedented supply of geographic data being made available in a very short time. But each of the services supplied its own slightly different interface to the data. People working to bring that data together and create ad-hoc applications in support of relief efforts would have to deal with the discrepancies.

 

Harmonizing the data

The Cascading map server offered by CubeWerx was able to connect to each of the other services offered, analyze their capabilities, and create a single, harmonized point of entry for application developers. Any map projections or image formats the downstream servers were unable to provide were automatically provided for them by the CubeWerx server. Any version of the WMS protocol they were unable to support was transparently provided.

Integration with Google Earth

CubeWerx Cascading WMS also implements a Google Earth interface allowing users of the service to benefit from the use of a tree style structure for selecting Map layers, a legend, and styling capability though the use of OGC Style Layer Descriptor (SLD) encoding. The benefits of cascading extend to this as well, since each of the cascaded servers automatically becomes available in the Google Earth interface.

So, what are the benefits of a cascading WMS?

  • It integrates WMS content and capabilities of each cascaded WMS service using a simple URL entry point; each WMS service remains deployed close at their data sources.
  • It can connect to all versions of OGC compliant WMS services; a client application accessing the service doesn't have to worry about differences between the many WMS versions deployed in the market.
  • The cascading WMS supports many image formats and will convert the data to your desired format.
  • The cascading WMS supports a large number of coordinate systems and will convert the data to your desired coordinate system.
  • The cascading WMS can support chaining at multiple levels. A loop detection mechanism prevents endless loops.