The OGC Web Coverage Service Specification and Its Implementation
Based on ISO definition, coverage is a function that by given a location on Earth specified by (x,y,z,t), it returns range values. Coverage data are data that can be defined by the coverage function. All remote sensing imagery belongs to coverage data.
In the past several years, the Open Geospatial Consortium (OGC) has been working on developing the Web Coverage Service (WCS) specification to facilitate the interoperable access to coverage data in the distributed web environment. The WCS Specification defines the application programming interface (API) for requesting coverage data from distributed sources. The first version of WCS specification which reached the status of OGC implementation specification (IS) is version 1.0, which was released in 2003.
In 2006, OGC updated the specification to WCS 1.1. Recent work in OGC has added two extensions into WCS 1.1. The first one is the transaction extension, which defines how WCS clients can request a WCS server import one or more new coverages into that server, update existing coverages, and/or delete existing coverages. The second one is the Web Coverage Processing Service (WCPS) Extension, which adds a raster expression language to WCS to allows analysis and processing of multi-dimensional grid coverage data over the World Wide Web. Resulting coverages can be transmitted directly or made available for download by URLs communicated to the client or to another geoprocessing service.
In the GeoBrain project, the Center for Spatial Information Science and Systems (CSISS) of George Mason University has implemented a WCS server based on WCS 1.1. Both extensions of WCS 1.1 have also been implemented. The WCS server is working with NASA HDF-EOS data operationally to provide interoperable, personalized, on-demand data access services to various data users.
