The development of a property information system for valuation using a geographical information system (GIS)

Property value is a function of locational, physical, legal and economic factors. The prevalent method of valuation is the comparison technique. Popular with valuers and favoured by the courts, the comparison method involves the analysis of properties similar to the one being valued in order to isolate and quantify individual influences on value. It is argued that geographical influences on value are handled implicitly during this process. This paper demonstrates that the spatial analysis of property data enhances the valuer's understanding of locational influences on property value. In order to examine the effect of location on retail property value in particular, legal and economic factors were held constant. Differences in value attributable to physical characteristics were reconciled using an 'intelligent' interface capable of undertaking simple comparison method analysis. Any remaining differences in value were attributed to locational factors. The paper demonstrates that it was then possible to display comparable evidence on a map and shade each property according to its locational value. This aids the valuer in the selection of comparable evidence based on locational criteria.