Why GIS for transportation system analysis?
GIS make it possible to display and visualize phenomenon such as traffic. For example, GIS can display on a map streets with various widths to represent different amount of traffic on these streets. In addition, GIS can be used to prepare data for analysis in ways not possible with traditional transportation modeling software. Fundamentals of GIS To be able to use TransCAD efficiently, it is necessary to understand some fundamentals of GIS. Two of the most important GIS concepts are introduced here to facilitate the understanding of the tutorial materials. More GIS concepts will be introduced throughout the quarter. • Maps are generated from a database Although GIS display maps, in most cases these maps are not stored in computers as image files. Maps are generated by GIS from a database with different tables. For example, each node in the map (Figure 1) is generated based on the coordinates in the Nodes table (on the upper right hand side). Each street link is generated by linking the
