Friday, May 2, 2008

What are geospatial web services and why should we use them?

Geospatial consumers need to easily ingest geo-data into a variety of desktop, Internet and 3D virtual globe applications they use in their daily work. Impediments in data delivery brought on by access or performance issues are thorns in the side of GeoJoe trying to be efficient…

On the other end of the pipe, data authors and publishers want to rapidly distribute data to their consumers (i.e. their customers, clients, users, purchasers, general public, etc.). These folks, from aerial data providers to national mapping agencies to the one-man geo-shop, need to deliver data in varying complexities and want to guarantee that the data can be immediately absorbed into applications in use by their customers.

To answer the demand for real-time, interoperable solutions for data sharing, the industry responded with the development of geospatial web services. Geospatial web services enable web-based access to quality geospatial data in varying formats and degrees of complexity. For example, a WMS, or Web Map Service, delivers a ‘portrayal’ of geographic information presented as a static map, rendered into picture formats such as PNG and GIF and useful for display and viewing purposes. Much more robust is a WCS, or Web Coverage Service. WCS supports ‘intact’ delivery of rich and intelligent raster data sources, in formats such as GeoTIFF and DTED, and usable in client-side rendering and as input into scientific models.

Also available are highly-specialized web services that allow for unique processes such as transformation of geographic coordinates, catalog querying, editing vectors and much more. An example is a WPS, or Web Processing Service, which defines a standard for publishing many and various geospatial processes, and also enables clients to find and bind to these services. A WPS can be any process, examples being change detections, measurements such as NDVI, and complicated models. The Open Geospatial Consortium (OGC) just approved the WPS standard this past February.

In streaming data via geospatial web services, actual datasets remain in one place while specific bits of information varying in complexity are streamed directly to requesting individuals across vast networks. For consumers, this means that data quality is increased as geospatial web services provide immediate access to the most current data stores. Moreover, data distributed via web services require no format translation on the client end, ensuring direct and hassle-free delivery into various applications (note: client applications must be able to consume web services). Data authors and publishers benefit as actual datasets may be updated in one place and streamed to multitudes of end user clients. In this model data is no longer duplicated and out-of date across various organizations. Furthermore, data ownership remains protected while data sharing is optimized. For both authors and consumers of geospatial data, the general flow of information across networks is exponentially improved, and faster data delivery means work gets done faster.

Note: the OGC leads development and implementation of standards for geospatial content and services, like those mentioned as examples in this post.

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