Isochrone maps can be created for different modes of transportation, e.g. Isochrone maps in the context of transport planning are essentially maps of accessibility where travel time is used as the cost metric. Isochrone maps have been used in transportation planning since at least 1887. An early example of this method was demonstrated by Clark in 1945. Isochrone and related maps are used to show the time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall. Recent techniques in visualization include linking travel times to network edges to show the paths accessible from a point rather than show the area accessible from a point. Increases in computation, data storage, and improvements in algorithms have facilitated the rapid generation of isochrones. Isochrones are currently typically computed by via generating shortest-path trees on network graphs, and then generating a convex hull around the accessible nodes. Isochrone maps are commonly used in the UK in connection with development control. Penck also created a series of maps that only depict the travel times of a certain transportation mode, for example Rail transport. Where as Galton and the Bartholomews published maps depicting the days or weeks it took to travel long distances, Albrecht further developed the idea to not only depict long distances and world travel but also smaller areas. An early isochrone map of Melbourne rail transport travel times, 1910-1922Įarly examples of Isochrone maps include the Galton's Isochronic Postal Charts and Isochronic Passage Charts of 18, Bartholomew's Isochronic Distance Map and Chart first published 1889 and Albrecht Penck's Isochronenkarte first published 1887.
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