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The Spatial Data Transfer Standard (SDTS) was designed to be capable of representing virtually any data model, rather than being a prescription for a single data model. It has fallen short of this ambitious goal for a number of reasons, which this paper investigates. In addition to issues that might have been anticipated in its design, a number of new issues have arisen since its initial development. These include the need to support explicit feature de® nitions, incremental update, value-added extensions, and change tracking within large, national databases. It is time to consider the next stage of evolution for SDTS. This paper suggests development of an Object Pro® le for SDTS that would integrate concepts for a dynamic schema structure, OpenGIS interface, and CORBA IDL.

The purpose of this research is to enable better understanding of current environmental conditions through the relations of environmental variables to the historical record. Our approach is to organize and visualize land surface model (LSM) outputs and statistics in a web application, using the latest technologies in geographic information systems (GISs), web services, and cloud computing. The North American Land Data Assimilation System (NLDAS-2) (http://ldas.gsfc.nasa.gov/nldas/; Documentation: ftp://hydro1.sci.gsfc.nasa.gov/data/s4pa/NLDAS/README.NLDAS2.pdf) drives four LSM (e.g., Noah) (http://ldas.gsfc.nasa.gov/nldas/NLDAS2model.php) that simulate a suite of states and fluxes for central North America. The NLDAS-2 model output is accessible via multiple methods, designed to handle the outputs as time-step arrays. To facilitate data access as time series, selected NLDAS-Noah variables have been replicated by NASA as point-location files. These time series files or ‘data rods’ are accessible through web services. In this research, 35-year historical daily cumulative distribution functions (CDFs) are constructed using the data rods for the top-meter soil moisture variable. The statistical data are stored in and served from the cloud. The latest values in the Noah model are compared with the CDFs and displayed in a web application. Two case studies illustrate the utility of this approach: the 2011 Texas drought, and the 31 October 2013 flash flood in Austin, Texas.

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The use of a semantically rich registry containing a Feature Type Catalogue (FTC) to represent the semantics of geographic feature types including operations, attributes and relationships between feature types is required to realise the benefits of Spatial Data Infrastructures (SDIs). Specifically, such information provides a more complete representation of the semantics of the concepts used in the SDI, and enables advanced navigation, discovery and utilisation of discovered resources. The presented approach creates an FTC implementation in which attributes, associations and operations for a given feature type are encapsulated within the FTC, and these conceptual representations are separated from the implementation aspects of the web services that may realise the operations in the FTC. This differs from previous approaches that combine the implementation and conceptual aspects of behaviour in a web service ontology, but separate the behavioural aspects from the static aspects of the semantics of the concept or feature type. These principles are demonstrated by the implementation of such a registry using open standards. The ebXML Registry Information Model (ebRIM) was used to incorporate the FTC described in ISO 19110 by extending the Open Geospatial Consortium ebRIM Profile for the Web Catalogue Service (CSW) and adding a number of stored queries to allow the FTC component of the standards-compliant registry to be interrogated. The registry was populated with feature types from the marine domain, incorporating objects that conform to both the object and field views of the world. The implemented registry demonstrates the benefits of inheritance of feature type operations, attributes and associations, the ability to navigate around the FTC and the advantages of separating the conceptual from the implementation aspects of the FTC. Further work is required to formalise the model and include axioms to allow enhanced semantic expressiveness and the development of reasoning capabilities.