Assessing geographic data usability in analytical contexts: Undertaking sensitivity analysis of geospatial processes

This paper addresses the comparative dearth of research on spatial data usability by employing sensitivity analyses to the findings from applying GIS-based accessibility models. Comparisons were made using approaches based on Euclidean distances and more sophisticated accessibility measures that utilise network travel distances: the latter incorporating measures of supply and demand by using innovative extensions to the Two-Step Floating Catchment Area method (2SFCA). To illustrate the sensitivity of findings from applying such models with a range of data sources, geographic accessibility to secondary schools was calculated for Output Areas in South Wales using a 2SFCA plug-in to ArcGIS(TM). By using different permutations of spatial data, for both the supply-and demand-side parameters in such models,differences in walking distances and FCA scores were sought in order to comment on the usability of such data sources. Preliminary conclusions are made on the appropriateness of such data sets in relation to different types of network-based accessibility modelling tasks