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Catchment Area

Catchment Areas show how far people can travel within a certain travel time or distance, using one or more transport modes.

1. Explanation​

Based on specified starting point(s), maximum travel time or distance, and transport mode(s), Catchment Areas visualize accessibility extent using real-world data. This provides insights into transport network quality, density, and extensiveness.

The catchment area can be intersected with spatial datasets, such as population data, to assess reachable amenities and identify accessibility coverage for inhabitants.

info

Catchment Area computation is available in specific regions.

When selecting a Routing type, GOAT displays a map overlay showing coverage. For Walk, Bicycle, Pedelec, and Car: over 30 European countries are supported. For Public Transport: Germany is supported.

Coverage for Walk, Bicycle, Pedelec & Car
Coverage for Public Transport

If you need analyses beyond these regions, feel free to contact us and we'll discuss further options.

2. Example use cases​

  • Which amenities are reachable within a 15-minute walk?
  • How many inhabitants have access to supermarkets within 10 minutes by bicycle?
  • What share of the population has a general practitioner within 500m?
  • How do workplace catchment areas compare between car and public transport? How many employees live within these areas?
  • How well are kindergartens distributed citywide? Which districts have accessibility deficits?

3. How to use the indicator?​

1
Click on Toolbox Options .
2
Under Accessibility Indicators, click on Catchment Area.

Routing​

3
Select the Routing Type for your catchment area calculation.

Configuration​

Considers all paths accessible by foot.

4
Choose whether to calculate the catchment area based on time or distance.

Time​

5
Configure Travel time limit, Travel speed, and Number of breaks.
walking-time configurations
Hint

For suitable travel time limits by amenity type, see the Location Tool from the City of Chemnitz.

Advanced Configuration​

By default, catchment areas are calculated as polygons. To adjust this, use the advanced configurations.

6
Click on Advanced Configurations Options Icon button. Here you can select the Catchment area shape. You can choose between Polygon, Network and Rectangular Grid.
  • It is a geometric representation of the catchments.
  • Easy-to-understand visualization
  • One polygon per step
Catchment Area Shape (Polygon) Public Transport in GOAT

You can choose Polygon Difference enabled which creates an "incremental" polygons for each step. On the other hand, disabled creates "full" polygons including all previous steps.

Starting Points​

7
Select the Starting point method: Select on map or Select from layer.
8
Choose Select on map. Click on the map to select starting point(s). You can add multiple starting points.
9
Click on Run. This starts the catchment area calculation from the selected starting point(s).
Hint

Calculation time varies by settings. Check the status bar for progress.

Results​

Once calculation finishes, the resulting layers are added to the map. The "Catchment Area" layer contains the calculated catchments. If starting points were created by map clicking, they're saved in the "Starting Points" layer.

Click on a catchment polygon to view details. The travel_cost attribute shows travel distance or time based on your calculation unit: time in minutes or distance in meters.

Catchment Area Calculation Result in GOAT

4. Technical details​

Catchment areas are isolines connecting points reachable from starting point(s) within a time interval (isochrones) or distance (isodistance). The calculation uses the appropriate transport networks for routing based on the selected travel mode.

Catchment areas are dynamically created in the frontend from a travel time/distance grid, enabling fast creation with different intervals on-demand.

Hint

For further insights into the Routing algorithm, visit Routing.

Scientific background​

Catchments are contour-based measures (also cumulative opportunities), valued for their easily interpretable results (Geurs and van Eck 2001; Albacete 2016). However, they don't distinguish between different travel times within the cut-off range (Bertolini, le Clercq, and Kapoen 2005), unlike heatmaps.

Visualization​

The catchment shape derives from the routing grid using the Marching square contour line algorithm, a computer graphics algorithm generating 2D contour lines from rectangular value arrays (de Queiroz Neto et al. 2016). This transforms the grid from a 2D array to a shape for visualization or analysis.

marching square

5. Further readings​

Further insights into catchment calculation and scientific background: this publication.

6. References​

Albacete, Xavier. 2016. “Evaluation and Improvements of Contour-Based Accessibility Measures.” url: https://dspace.uef.fi/bitstream/handle/123456789/16857/urn_isbn_978-952-61-2103-1.pdf?sequence=1&isAllowed=y

Bertolini, Luca, F. le Clercq, and L. Kapoen. 2005. “Sustainable Accessibility: A Conceptual Framework to Integrate Transport and Land Use Plan-Making. Two Test-Applications in the Netherlands and a Reflection on the Way Forward.” Transport Policy 12 (3): 207–20. https://doi.org/10.1016/j.tranpol.2005.01.006.

J. F. de Queiroz Neto, E. M. d. Santos, and C. A. Vidal. “MSKDE - Using Marching Squares to Quickly Make High Quality Crime Hotspot Maps”. en. In: 2016 29th SIBGRAPI Conference on Graphics, Patterns and Images (SIBGRAPI). Sao Paulo, Brazil: IEEE, Oct. 2016, pp. 305–312. isbn: 978-1-5090-3568-7. doi: 10.1109/SIBGRAPI.2016.049. url: https://ieeexplore.ieee.org/document/7813048

https://fr.wikipedia.org/wiki/Marching_squares#/media/Fichier:Marching_Squares_Isoline.svg

Majk Shkurti, "Spatio-temporal public transport accessibility analysis and benchmarking in an interactive WebGIS", Sep 2022. url: https://www.researchgate.net/publication/365790691_Spatio-temporal_public_transport_accessibility_analysis_and_benchmarking_in_an_interactive_WebGIS

Matthew Wigginton Conway, Andrew Byrd, Marco Van Der Linden. "Evidence-Based Transit and Land Use Sketch Planning Using Interactive Accessibility Methods on Combined Schedule and Headway-Based Networks", 2017. url: https://journals.sagepub.com/doi/10.3141/2653-06

Geurs, Karst T., and Ritsema van Eck. 2001. “Accessibility Measures: Review and Applications.” RIVM Report 408505 006. url: https://rivm.openrepository.com/handle/10029/259808