AwaP-IC – An Open-source GIS Tool for Measuring Walkable Access
AwaP-IC is a QGIS tool that calculates the Area-weighted average Perimeter (AwaP) and Interface Catchment (IC), which combined, capture the capacities of urban morphologies to enable and attract pedestrian movement
AwaP and IC are QGIS plugins that calculate the Area-weighted average Perimeter (AwaP) and Interface Catchment (IC), two measures developed by Pafka & Dovey (2017), that combined, capture the capacities of urban morphologies to enable and attract pedestrian movement. While AwaP and IC should be considered together in the analysis of walkable access, in the current version of the software the two measures are provided by distinct plugins.
AwaP is a measure of urban permeability, that calculates the average perimeter of urban blocks within a study area, weighing the perimeter of each block by its area. This way the impact of a large block will be proportional with the share of the study area it occupies, and its effect as a major-barrier to movement is not lost in the average. The lower the AwaP, the easier is to walk through the urban fabric. An AwaP of 400m corresponds to a square block of 100x100m, often taken as the maximum block-length that still allows good permeability.
IC calculates the total length of public/private interfaces reachable from a starting point and within a given walking distance. IC is relevant for walking as most urban attractions, such as dwellings, shops and workplaces, are accessed through the public/private interface, where buildings meet the street. High IC values indicate high capacity for accommodating urban attractions. Together, these two measures account for both street width and block size, measuring both walkable access and what one gets access to.
Unlike GIS tools based on models that abstract streets to axial lines, by employing new algorithms and spatial computation techniques, AwaP-IC analyses actual urban morphologies, based on cadastral maps delineating public and private land. This can empower a new stream of urban morphological studies with the computational power of GIS. As an open source tool, it can be further developed for use in urban mapping and to streamline the analysis of large datasets.
The plugins are available from the QGIS plugin repository: AwaP, IC
Reference:
Majic I. & Pafka E. (2019) AwaP-IC - An Open-Source GIS Tool for Measuring Walkable Access. Urban Science 3(2): 1-14.
Pafka E & Dovey K. (2017) Permeability and Interface Catchment: Measuring and Mapping Walkable Access. Journal of Urbanism 10(2): 150-162.
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