Open space index: a GIS-based tool for assessing human penetration of a landscape

In light of the rapid and continuous growth of the built environment worldwide and its attendant ecological impact, increasing the size and distribution of open space in urban areas is recognised as one effective way to reconcile the social and ecological objectives of society. However, there is no simple and objective indicator to measure open space that can be used for creating and maintaining sustainable landscapes. The paper introduces a metric, open space index (OSI), that measures the amount of space unpenetrated by the built environment. The metric is calculated by measuring the shortest distance between any location and the nearest built environment using a Geographic Information System. The metric is illustrated using two counties of the greater Twin Cities Metropolitan Region of Minnesota. The sensitivity of OSI to the size, shape, and spatial configuration of the built environment suggests that the metric can serve as an important planning tool for reconciling conservation and development in a wide range of contexts.