Volume 26 • No 09 • 2003
ISSN 0742-468X • Since 1978
On-line Since 2000
Open GIS Standards Move Forward
There is a move afoot to standardize GIS. You know all about standards, don’t you? They are more often than not established by people who cannot catch the front runner. In our world of GIS we have something called the Open GIS Consortium (http://www.opengis.org) It is an organization that describes itself as “a member-driven, non-profit international trade association that is leading the development of geoprocessing interoperability computing standards.”
Interoperability seems to be the latest buzz word that has just about replaced the word “standards.” For one thing it sounds less threatening. For another, unlike strict standards interoperability seems to leave more room for growth and future development. From an end–user perspective it doesn’t matter that much. What we want is the ability to use our chosen software on any geo–file, no matter which platform created it.
Besides, who wants to tell their clients that their software can read ESRI’s shape files, when they can say that it adheres to the OGC’s interoperability standards?
Web news from Spain
While the rest of us were raking the autumn leaves the technical and planning committees of the OGC were toughing it out in Spain. As a result, the Open GIS Consortium, Inc. (OGC) moved two OpenGIS® Web Services specifications through the approval process. The committees adopted the Web Coverage Service Specification, which defines how to access gridded geographic data. Also, they moved the Web Terrain Service Specification, which details how to render vector and raster data as a 3D view, to Request For Comment status.
The Web Coverage Service (WCS) provides access to intact, raw data such as imagery, digital elevation matrix (DEM) and other types of gridded data
Web coverage, what’s that?
If you want a static map, you use the specs of the Web Map Service (WMS). On the other hand, Web Coverage Service provides only data access. Typically client-side applications will model, analyze and render the data. WCS was submitted by BAE SYSTEMS – Information Systems Sector (U.S.), Commonwealth Scientific and Industrial Research Organisation (CSIRO) Exploration and Mining (Australia), CubeWerx Inc. (Canada), German Aerospace Center – DLR (Germany), Galdos Systems Inc. (Canada), George Mason University (U.S.), Intergraph Mapping and Geospatial Solutions (U.S.), IONIC Software (Belgium). MITRE Corporation (U.S.), National Aeronautics and Space Administration (U.S.), PCI Geomatics, Inc. (Canada), Polexis, Inc. (U.S.), Raytheon Company (U.S.), United States Army Corps of Engineers, and the United States Geological Survey. The approved specification is publicly available for download at http://www.opengis.org/specs/?page=specs.
But what is the Web Terrain Service all about?
The Web Terrain Service (WTS) specification defines a standard interface for requesting three-dimensional terrain scenes from a server capable of their generation. A “3D scene” is defined as a 2D projection of three-dimensional features into a viewing plane. The membership approved WTS as a Request for Comment. OGC invites any interested parties to review the document, now available at http://www.opengis.org/specs/?page=requests&request=rfc18, and suggest additions or changes.
According to the OGC “A Web Terrain Service (WTS) produces views of georeferenced data. We define a ’view’ as a visual representation of geodata; a view is not the data itself. These views are generally rendered in a 2D pictorial format such as Portable Network Graphics (PNG), Graphics Interchange Format (GIF) or Joint Photographic Expert Group (JPEG) format. This specification standardizes the way in which clients request views and the way that servers describe their data holdings. Two required operations are defined:
- GetCapabilities: Obtain service-level metadata, which is a machine-readable (and human–
readable) description of the WTS's information content and acceptable request parameters.
- GetView: Obtain a 3D scene whose geospatial and dimensional parameters are indirectly defined.”
Conclusion
GIS grew up without many standards. Developers pushed the envelope and kept changing the stationery. The idea of proprietary software was not new to GIS. In fact it was a way of business in the IT community. The web changed all that. In fact most college students cannot understand that there was once a time when computers of different vendors could not interact with one another. They have grown up in a world of cross-platform compatibility.
For GIS to succeed on the Web, it must work across all platforms, browsers, operating systems, and whatever else comes down the pike. Frankly, interoperability of desktop GIS is far less important than interoperability across the web. Encourage our suppliers to participate in the evolving standards and insist on compliance. Get acquainted with the OGC: Visit the OGC website at http://www.opengis.org.
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