A spatial data model for urban spatial-temporal accessibility analysis.

Time geography represents the uncertainty of the space-time position of moving objects through two basic structures, the space-time path and space-time prism, which are subject to the speed allowed in the travel environment. Thus, any attempt at a quantitative time-geographic analysis must consider the actual velocity with respect to space. In a trip, individuals tend to pass through structurally varying spaces, such as linear traffic networks and planar walking surfaces, which are not suitable for use in a single GIS spatial data model (i.