Standardized Coverage Interfaces

Making GEONETCast data available through the web, it is either possible to connect such service directly to the data server, or to insert the GEONETCast data through the transactional interface of the service over the web. In both cases the changes and updates of the data need to be monitored. In the case of a direct link between the data server and the service, the configuration of the service needs to be updated to serve the data according to the latest changes. The service then directly accesses the data, whenever it is requested. This direct connection does not result in any additional computational effort and also does not result in redundant storage of data. Redundant storage, however, is the effect when updating the service through its transactional interface. For some cases, storing the data directly on the service through its transactional can be considered for performance reasons, if for instance the service manages the data internally through a database and is thereby able to apply indexing strategies. Additionally, using the transactional interface, it is possible to connect to any compliant WCS instance.

OGC compliant frameworks

First we had to decide on an implementation of the OGC interface specification, which is able to serve raster data through a WCS service and also supports requests restricted to spatial extentsion, time resolution and certain subchannels.

After testing the Geoserver (mainly because of java implementation and good operating experience in using it for WFS), we decided to switched to Mapserver mainly because of a benchmark test found on the web (Erdas Imager Server vs. Geoserver vs. Mapserver): http://blog.webmapper.com.au/image-server-benchmark/comment-page-1/

In addition we collected several reasons / expirience made by ourself: GeoserverVsMapserver

Features of Mapserver

• serve the data through WCS interface (data access) as well as WMS interface (data portrayal) using on and the same data basis- users are thereby able to inspect the data (using WMS interface) without downloading it.
• able to read serveral input formats, in particular multichannel geotiff format is supported and channel ranges automatically mapped and subset on the fly
• support of time dimensions for a single coverage by reading it on-the-fly out of database (either postgis or shape/dbf file), where different timestamps referring to their related geotif coverage

Configuration of Mapserver

Howto

• setup Mapserver on a windows system can be read in our MapserverInstallation guide
• setup the transactional interface service (configuration of mapserver) in order to serve data through WCS and WMS interface is illustrated in our MsgHritInterface Usecase

-- JohannesTrame - 2010-09-23