The conceptual framework underlying the Baltimore Ecosystem Study (BES) relates spatial heterogeneity to human ecosystem processes. The first two of the three main questions driving the BES require the quantification of spatial heterogeneity in the Gwynns Falls Watershed (the focal watershed of the BES). The first question is: "How do the spatial structure of socio-economic, ecological, and physical factors in an urban area relate to one another and how do they change through time." To address this question the socio-economic, ecological, and physical patches within the study area must be defined. Several projects within the BES have taken on this task. Approaches are focused on emphasizing socio-economic, ecological, or physical features as patch delimiters. The eventual goal is to integrate approaches and develop a synthetic patch delimitation scheme for the BES study area.