A narrative analysis of the 2SFCA and i2SFCA methods

ABSTRACT

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 ${\mathrm{R}}_j$ 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.

KEYWORDS:

• Spatial accessibility
• market potential
• spatial interaction
• 2SFCA

Acknowledgements

The authors thank Professor Fahui Wang for making publicly available the Florida dataset used in this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Jie Lin

Jie Lin is Associate Professor at Zhejiang University. His research interests focus on GIScience, spatial analysis, and their socioeconomic applications. His contribution to this paper includes algorithm coding, data preparation and process, write-up, and paper revisions.

Gordon Cromley

Gordon A. Cromley is the GIS Lab Director at Dickinson College. His research interests focus on GIS applications for Digital Humanities and Critical Cartography. His contribution to this paper includes the narrative critique, write-up, and paper revisions.