VISUALIZING STOCHASTIC CATCHMENTS IN GEOGRAPHICAL NETWORKS

This paper presents an approach to visualising the area of the catchme nt for a service facility within a network which allows recognition of variability in travel time along the different road segments. By way of illustration fifteen different road conditions are modelled, for th e 10 minute travel zone from the Leicester Royal Infirmary. The catchm ents at each state are then summed, and the resulting composite catchm ent is visualized as grey scale images, with zones of equal travel tim e appearing in similar greys. The observed pattern is of a core-periph ery catchment, the core having high probabilities of being within a ce rtain travel time, and the periphery having increasingly low probabili ties. Four factors which may influence the size and shape of the zones are described. Finally, discussion centres on the shortcomings of bot h raster and vector data structures for completing the proposed proced ure.