This study examines the narrative(s) that surround the development of the Two-Step Floating Catchment Area (2SFCA) family of GIS-based accessibility statistics. It identifies what has been omitted from the pre-GIS era in its discourse and presents a parallel but alternative narrative behind these statistics. The results suggest that the ‘crowdedness’ metric from the i2SFCA can more broadly be viewed as a form of market potential, and the 2SFCA and i2SFCA are normalized, singly supply-constrained and singly demand-constrained spatial interaction models, respectively. It postulates that the Rj values calculated in the 2SFCA are not real supply-to-population ratios, but the inverse of the market potential metric associated with the i2SFCA is, and this inverse value can be used to develop an adjusted supply accessibility metric. This enables the 2SFCA family of supply accessibility metrics also to account for congestion at service sites. Results using the adjusted and congested supply accessibility metrics suggest that less densely populated areas may not be at a disadvantage with respect to the supply of services once congestion is taken into account. The adjusted and congested supply accessibility metrics also have a complementary cost accessibility metric that when used in tandem measure the size and efficiency of supply availability.

Lin, Jie, and Gordon Cromley. A Narrative Analysis of the 2SFCA and i2SFCA Methods. International Journal of Geographical Information Science 36, no. 5 (2022): 943-967. https://www.tandfonline.com/doi/full/10.1080/13658816.2021.1986831

Gordon Cromley is Director of the Spatial Literacy Center and GIS Specialist at Dickinson College.

For more information on the published version, visit Taylor and Francis's Website. https://www.tandfonline.com/doi/full/10.1080/13658816.2021.1986831

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