||In this paper it is proposed that geographic information systems should be used to support decisions about urban management, development and qualification. The goal of the paper (which is based upon a project I am presently developing in Oporto University), stands upon the establishment of a real estate price level function, which depends upon the accessibility to polarized urban zones, among other variables. The GIS assessment of this subject looks forward to give an analysis tool that supports urban decisions. The permanent updating of information through this tool allows the implementation of policies longing to promote high quality standards of urban life. The paper begins by the theoretical analysis of real estate policies, particularly in what concerns urban polarized centres. Then it is established an econometric model that explains how real estate prices are dependent upon the space and time accessibility to a polar zone, the activities distribution, temporal inertia of activities, and public investments. This model, which is presently being applied to the Oporto city, in Portugal, with successful results, reveals high potential to evaluate the consequences of urban policies, and is adaptable to other cities in polarized urban regions, but it needs to be permanently feed and controlled through the updating of basic information, so it is proposed the establishment of an observatory with a certain number of observable variables (such as spatial activities distribution, temporal inertia of activities, and public investments). Adopting an appropriate way of representing each of these variables in the town map, the process described may also be used to support the corresponding fields´strategic gap´s decisions.