Wednesday, December 16, 2009

NHD SLD opens up world of WMS and Google Earth

A prototype Styled Layer Descriptor for National Hydrography Data (NHD) has been tested in Google Earth - opening up the world of OGC Web Map Services (WMS) even more for Google Earth users.

The SLD was developed by USGS and deployed as part of prototype WFS and WMS services. The capability highlights how SDI data providers can use the same underlying data to generate different types of maps - like a transparent overlay of hydrography on Google Earth - using a standards-based XML language from OGC.

The NHD SLD is based on cartographic specifications and USGS Symbol libraries were used to render geographic features in a cartographic quality map. To produce the SLD XML, map symbology documents '6psym403.pdf' and 'topomapsymbols.pdf' were used as templates to generate SLD encodings for NHD styles. Descriptions of the technical development effort and examples are available - as well as the prototype SLD encoding. The deployment is powered by standards-based WMS which can generate dynamic, scale-dependent maps and map legends as transparent overlays in Google Earth.

- Jeff


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