Numerous federal agencies produce official statistics made accessible to ordinary citizens for searching and data retrieval. This is frequently done via the Internet through a Web browser interface. If this data is presented in textual formatT T he SAND Spatial Browser is part of the SAND System whose server side contains a spatial database system that facilitates organization (that is, indexing) of spatial and nonspatial data [1] to support efficient query processing. This database system handles any two or higher dimensional data with extent (for example, country boundaries, river paths), as well as point data (for example, city locations). It facilitates the response to queries involving this data such as finding the closest hazardous waste site to the border of a particular state.Users access and manipulate spatial and nonspatial data using the SAND Spatial Browser in a manner similar to that used in spreadsheets where the map plays the same as a relation in a relational database management system. In particular, operations can be specified as compositions of maps with the output of one or more operations serving as input to other operations that can be saved for use as input to

The use of scripting makes it possible to overcome many important difficulties in the development of database applications. By extending a general-purpose scripting language with constructs derived both from the database kernel and from the intended application domain, issues such as query processing and user interfacing can be approached in an economical and flexible way. This is illustrated by describing our experience with SAND-Tcl, a scripting tool developed by us for building spatial database applications. SAND-Tcl is an extension of the Tcl embedded scripting language with the constructs of the SAND environment for developing applications involving both spatial and non-spatial data. SANDTcl acts as a "glue" to hold together all the subsystems of SAND. In fact, query evaluation plans are SAND-Tcl programs (or scripts) which are written on-the-fly by SAND in response to a query defined by the user. This permits the rapid prototyping of algorithms and makes SAND a useful tool both for applications and research. The focus is on data storage, retrieval operations, and spatial indexing. Implementations of operations such as spatial selection, ranking, and spatial join are given. In addition, tools are described to make possible the construction of graphical user interfaces to a spatial database as well as providing users the ability to view and interact with spatial objects in a graphical manner. This is achieved through the use of SAND-Tcl scripts and the Tk graphical user interface toolkit which is tightly coupled to Tcl.

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We present a practical approach for implementing the Projected Tetrahedra (PT)

We present an efficient Graphics Processing Unit GPU-based implementation of the Projected Tetrahedra (PT) algorithm. By reducing most of the CPU-GPU data transfer, the algorithm achieves interactive frame rates (up to 2.0 M Tets/s) on current graphics hardware. Since no topology information is stored, it requires substantially less memory than recent interactive ray casting approaches. The method uses a two-pass GPU approach with two fragment shaders. This work includes extended volume inspection capabilities by supporting interactive transfer function editing and isosurface highlighting using a Phong illumination model.