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Robin Fegeas, USGS, Reston, VA

Topic: Just What is SDTS and What Does It Really Need?

Email: arctur@acm.org and rfegeas@usgs.gov

Web: http://www.lsl.co.uk/~arctur

What are the benefits of the SDTS? Any data model can be represented in SDTS. Profiles constrain data models down to something more domain specific chosen around levels of topology. The standard supports virtually any application data model in a vendor-independent format. 0D, 1D, and 2D topological models are represented. There are feature-to-feature relationships (although not a clear definition of what a feature is in SDTS). SDTS has a useful separation of geometry from graphic representation, feature-level security, data quality information, and thematic, temporal and other groupings of data.

What does SDTS need? There is not a precise definition of geographic features and there is an unambiguous declaration of the relationship between attributes and spatial objects. More profiles are needed to support most useful categories of data models. Currently there is not support for multiple profiles within a dataset, such as having feature or object within a topo profile refer to a feature or object in a transportation data set. There needs to be support of subtiling within a dataset and the ability to do incremental updates to a base dataset, as well as allow for direct, rapid, record-level access to data.

What is next? The emergence of the OpenGIS standards and the USGS DLG-F standard may solve some of what is lacking in SDTS. What we can do now is fix the known problems with SDTS and work to harmonize SDTS with OpenGIS and DLG-F.

A general consensus from the audience was topology should be taken out of SDTS to help simplify the data or create a profile that does not require topology. Dr. Arctur is interested in working with other groups to develop an object-oriented profile.