Data Structures in UrbanSim

UrbanSim has evolved over several years, and so have the data structures used in it. Until 2005, most applications used a data structure based on a grid overlaid on the study area. Most UrbanSim applications to date have used this approach to structuring the data. Various limitations of the gridcell approach led to the more recent adoption of a parcel-based data structure. This section explains the fundamental differences in these data structures, and assesses their relative merits. Both are still used and supported approaches, though the advantages of the parcel approach are fairly significant. We begin with an overview of the three different data structures that UrbanSim now supports: gridcells, parcels, and zones.