Southern California is one of the largest urbanised regions of the world and extends over 39171 square miles with a total population of over 15 million. The Southern California Association of Governments (SCAG) is the regional transportation planning agency for 188 cities ranging in size from Los Angeles (3.5 million population) to small communities with fewer than 50,000 people. SCAG collects a large amount of data which is stored in the GIS. This paper describes the transportation GIS project implemented by SCAG which integrates the agency's transportation street network, model networks, land use, demographic and employment data sets. The data sets are accessed by the SCAG Geographical Data Interface (SGDI). The SGDI provides a user-friendly interface to allow the planners to access, query, display, analyse and plot the transportation and planning data. The paper focuses on the integration of the transportation model networks (highway and transit networks) and the GIS. The integration of networks data, referred to as network conflation, is an emerging technique in GIS for transportation and is especially useful in linking schematic transportation model networks to actual street maps. Network conflation involves a number of the data conversion steps. These are described in the paper.
Samenvatting