Linear referencing

Abstract: Network data structures were one of the earliest representations in geographic information systems (GIS), and network analysis remains one of the most significant and persistent research and application areas in geographic information science (GIScience). Network analysis has a strong theoretical basis in the mathematical disciplines of graph theory and topology, and it is the topological relationships inherent in networks that led to revolutionary advances in GIS data structures. Networks can represent an alternative datum for geo-location in the context of linear referencing and support a set of tools for graphical display known as dynamic segmentation. Many network location problems are among the most difficult to solve in terms of their combinatorial complexity and, therefore, provide both a challenge and an opportunity for GIScience researchers. Because elements of network analysis appear in a wide range of academic disciplines—from physics, to sociology, to neurobiology—there are ample opportunities...

Abstract: Sharing of digital road map databases within and among organizations is dependent on translating user requirements to a data model that supports linear and non-linear location referencing systems. This paper examines issues of creating such a data model with the intent of sharing digital road map databases, and suggests implementation choices that can accommodate a range of applications. The proposal is best characterized as a geographic information system for transportation (GIS-T) enterprise data model suitable for organizations responsible for any and all modes of transportation; e.g. aviation, highways, public transit and railways. The proposed data model may be sufficiently robust to support intelligent transportation systems (ITS) map database interoperability by maintaining independence among the geographic datum, the events that occur on the transportation system, the geometry to represent the system cartographically, and the paths through the system. Sample physical database designs are provided to show how the model might be implemented.

Abstract: This paper develops a framework and principles for sharing transportation data. The framework is intended to clarify roles among participants, data producers, data integrators, and data users. The principles are intended to provide guidance for the participants. Both the framework and the principles are based on an enterprise geographic information systems-transportation (GIS-T) data model that defines relations among transportation data elements. The data model guards against ambiguities and provides a basis for the development of the framework and principles for sharing transportation data. There are two central principles. First is the uncoupling of graphics, topology, position, and characteristics. Second is the establishment of a schema for transportation features and their identifiers. An underlying principle is the need for a common data model that holds transportation features, not their graphical representations, as the objects of interest. Attributes of transportation features are represented as linear and point events. These are located along the feature using linear referencing. Sharing of transportation data involves exchange of relevant transportation features and events, not links and nodes of application-specific databases. Strategies for sharing transportation features follow from this approach. The key strategy is to identify features in the database to facilitate a transactional update system, one that does not require rebuilding the entire database anew. This feature-oriented enterprise GIS-T database becomes the basis for building separate application-specific network databases.

Abstract: This digest describes a consensus location referencing data model that was developed under NCHRP Project 20-27(2), "Systems and Applications Architecture for GIS-T" The model allows linkages to various types of data over all modes This information will be of use to persons involved with the design and implementation of field location referencing systems as well as the structuring of agency databases for location referencing