Implementing the Enterprise GIS in Transportation Database Design

Earlier articles by the authors described the primary database design approaches that have been and are being used in geographic information system applications for transportation. These articles proposed a theoretical model for an enterprise geographic information system environment for transportation agencies. This follow-up article provides detailed guidance on building a multimodal transportation feature database using relational database concepts. 2000, 1998, Dueker and Butler 1999, 1998). These articles present theoretical and implementation aspects of an Enterprise GIS-T Data Model that includes four primary components: 1. a facility inventory comprising jurisdiction, transportation features, event points, linear events, point events, and intersections; 2. a network that includes nodes, links, traversals, and traversal segments; 3. a measurement datum consisting of anchor points, anchor sections, reference objects, and geographic points; and 4. cartography, which includes (in the simplified version discussed here) base map strings, linear event strings, line segments, point symbols, and cartographic points. The list of components is essentially an “all of the above” response to the existing structures of legacy transportation information systems and current GIS product lines (Butler and Dueker 2000). At the same time, the unbundled approach of the system allows system designers to pick the elements that are needed for a particular application (Dueker and Butler 1998). For example, Want to draw a map of an existing highway inventory? It is necessary to: 1. Choose a GIS platform that supports dynamic segmentation. 2. Establish a one-to-one relationship between each transportation feature map object and its corresponding feature in the inventory. This is accomplished by constructing the object and then attaching the transportation feature identifier in the inventory database. 3. Assign measures for beginning and ending points for linear objects representing linear transportation features. 4. Use the dynamic segmentation function to create a cartographic object for each linear event or to position point events.