The Data Model And Realization Of GIS-T On ITS Information-exchange Platform

Intelligent Transportation Systems (ITS) are being considered internationally as a means of resolving the traffic problems and controlling the environmental pollutions that caused by the traffic problems. ITS information-exchange platform can realize transportation information collection and sharing. It can also support decision-making and publish transportation information. Geographic Information System for Transpor- tation (GIS-T) is a support system that store and apply geographic and transportation data. And it is an essential technology of ITS information-exchange platform. The design for GIS-T data model plays an important role in the realization on function of GIS-T.The traditional Arc-Node and Entity-Oriented data models cannot express the world exactly, so it brings the redundancy of data and the low efficiency on complexly manipulating spatial data. In the feature based GIS data model, geographic entity (in this paper it is called feature) is a key element, which is used to express, to organize and to store geographic space. It gives a more natural representation of real world, takes seriously the semantic and temporal attributes related with geographic features, deals with layer technology properly, and pays attention to the multi-scale specialty of the geographic features.Linear referencing and dynamic segmentation technologies are introduced into the feature based GIS data model to represent and manipulate the spatial or temporal changes of an event along a linear feature. The realization of the ITS application is more or less depend on lane, and the accuracy of the GPS is not sufficient to locate a vehicle on a specific lane. Consequently, lanes are used as basic features to analyze the traffic network, and integrated lanes are used as display and coordinates referencing features.In the Object Relational Database Management Systems (ORDMS), the technologies of managing data are mature and popular, and the technologies of defining new data type are flexible. So it is chose to realize the feature based GIS-T data model. It extends temporal and spatial interval with a new data type to represent and manipulate spatial and temporal changes over a linear feature. Also it provides Object Query Language to query and operate the changes of the events.According to the need for the ITS platform, the basic geographic and transportation feature themes are concluded, the database designs for different features are given, some basic and advanced functions of the GIS-T are realized.