Reconciling incompatible zone systems in metropolitan planning

Observers have long noted large gaps between planning research and planning practice. Geographic Information Systems (GIS), for example, are now widely used in urban planning, but in relatively simple ways that fall far short of their analytical potential. This dissertation examines the gap between research and application in the use of GIS in planning practice. Planners are sometimes called upon to perform spatial data transformation, a GIS procedure used to convert data from one set of zones (system A) to a different set of zones (system B) where systems A and B have incompatible zone boundaries. Spatial data transformation is typically performed by overlaying source zones with target zones and interpolating target zone data from source zone data. The simplest methods are quite crude, and often introduce significant error, while more sophisticated methods tend to transform data with far less error. Because metropolitan planning organizations (MPOs) typically convert data from census zones to transportation analysis zones (TAZs) for transportation analyses, a survey was sent to all 350 MPOs in the U.S. to collect information about their spatial data transformation activities. The survey reveals that 60 percent of MPOs perform spatial data transformation more than once per year, usually using the simplest, most error-prone methods. The survey data is used to develop several models which show that MPOs' frequency of performing spatial data transformation is, not surprisingly, positively associated with area population, land use intensity, TAZ structure, and staff GIS expertise. Other models suggest that GIS expertise in particular is positively associated with use of more sophisticated methods for spatial data transformation. Given the lag in application of new GIS techniques among planners, it is perhaps not surprising that practicing planners tend to favor simpler methods of spatial data transformation, despite the widely-documented shortcomings of such techniques in the literature. These findings suggest that the gap between research and application in the utilization of GIS in planning practice will require both more advanced training of planners using GIS, and, perhaps more importantly, greater sophistication among the “consumers” of GIS planning analyses—non-GIS planners, public officials, and the general public. Until then, it appears likely the gap between the rapidly advancing spatial analysis capabilities of GIS and their application in practice will continue to widen.