Comparative approaches to measuring food access in urban areas: the case of Portland, Oregon.

GIS methods are used to construct measures of food access for neighbourhoods in the Portland, Oregon, US metropolitan area and the sensitivity of such measures to methodological variation is examined. The level of aggregation of data inputs is varied and the effect of using both Euclidean and street network distances is tested. It is found that, regardless of the level of geographical disaggregation, distance-based measures generate approximately the same conclusions about the distribution of food access in the area. It is also found that, while the relationship between street network and Euclidean distances varies with population density, measures computed with either construct generate the same relative patterns of food access. These findings suggest that results from food access studies employing disparate methodologies can often be compared.