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Using network segments in the spatial representation of travel time isochrones

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NACIS 2016 Presentation
Jeff Allen, University of Toronto
Steven Farber, University of Toronto Scarborough
Isochrones are often used for visual analysis of mobility and accessibility in urban areas. We will discuss an alternative method to conventional isochrones; using computed travel times to classify network segments rather than generating isolines or polygons. We will outline the data, tools, and geoprocessing steps required to make these kind of maps as well as discuss visualization considerations for different scales, subject matter, and for static and interactive maps. Further discussion will include their advantages and disadvantages when compared to conventional isochrones, particularly in terms of classification options and mapping in conjunction with other data. Finally, we will comment on how this method results in potential benefits for subsequent spatial analysis and how it can be scaled for multiple origin points, travel modes, departure times, and transit scenarios.

Published in: Design
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Using network segments in the spatial representation of travel time isochrones

  1. 1. Using network segments in the spatial representation of travel time isochrones
  2. 2. Isochrones Iso = Equal Chrone = Time
  3. 3. https://upload.wikimedia.org/wikipedia/commons/8/86/Isochronic_Passage_Chart_Francis_Galton_1881.jpg
  4. 4. https://archive.org/details/atlasofcommercia00bart
  5. 5. https://en.wikipedia.org/wiki/File:Map_of_Melbourne_and_environs_minimum_railway_or_tramway_time_zones.jpg
  6. 6. https://en.wikipedia.org/wiki/File:Map_of_Melbourne_and_environs_minimum_railway_or_tramway_time_zones.jpg
  7. 7. Existing Tools: ArcGIS Network Analysis PostGIS + pgRouting OpenTripPlanner Dozens of Web Applications etc. General Steps 1 - Create a Network Graph 2 - Compute travel time from a point to network vertices 3 - Generate shapes or surface for specific travel times 4 - Visualize output Output: Isolines, polygons, vector grids, or rasters that represent the AREA that is accessible from a point (or points)
  8. 8. A structural alternative: General Steps 1 - Create a network graph 2 - Compute travel times from a point to network vertices 3 - Generate shapes at specific travel times 3 - Join travel times to edges 4 - Classify / visualize output Using network segments in the spatial representation of travel time isochrones.
  9. 9. Output Data Structure:
  10. 10. Questions 1 - How can this technique be applied? 2 - How can it lead to new insights about our data? 3 - When is it preferable over conventional isochrones? or
  11. 11. 1 - Mapping Differences in Travel Times: By Travel Mode By Time of Day For Different Transit Agencies
  12. 12. 1 - Differences in Travel Times
  13. 13. 1 - Differences in Travel Times
  14. 14. v 2 - Combining with Areal Data
  15. 15. 3 - Potential Path Areas
  16. 16. 4 - Transit Maps:
  17. 17. 4 - Transit Maps:
  18. 18. 4 - Transit Maps:
  19. 19. 5 - Travel Surveys:
  20. 20. 5 - Travel Surveys:
  21. 21. 5 - Travel Surveys:
  22. 22. Some code & maps are on my github page at jamaps.github.io Thank You!

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