Use of 3D cadastral data for real estate mass valuation in the urban areas

An assessment of real estate value is a prediction of its value based on experience, and taking into consideration its spatial, physical, legal and economic factors. Location has great influence on value because the real estate is being significantly determined by its spatial properties. In the urban areas, correlation between the value of real estate and its location is very complex and it depends on many subjective and objective factors. Mass valuation is a procedure which, based on objective factors, using statistical methods assesses the value of a big number of real estate. Modern, Computer-Assisted, real estate valuation systems worldwide are based on the existing spatial data, a combination of land administration and topographic data, along with the market factors. Efficient functioning of a real estate cadastre, as the basic infrastructural system, facilitates significantly the planning and accomplishment of economic and other activities linked to real estate. This paper examines the possibilities of mass real estate valuation, based on 3D Vector Terrain Model, created from the digital cadastral map (DCM) of the cadastral municipality of Centre, provided by the City of Zagreb Office for Cadastre and Geodetic Works and topographical data. As in cadastre, basic unit of realised real estate valuation system is real property, which can generally be seen as land, buildings, and whatever is attached or affixed to the land. In the lack of true 3D cadastral data models and data, procedures for real estate valuation were based on model which consists of 3D physical objects made from 2D cadastral data (land parcels and buildings) and topographical data – elevation. Data were modelled, stored and analysed using the combination of PL/SQL procedures and Oracle 11g SDBMS built-in spatial functions. This paper concentrates on further development of visibility analysis calculation of real estate, which requires more detailed 3D physical model. The idea behind modelling the influence of this factor on real estate valuation is the assumption that a real estate with a bigger visibility polygon, i.e. a better view, has a bigger market value than the same real estate with a smaller visibility polygon. On the part of the model, each part of 3D property unit were manually modelled into smaller parts according to a plan of separate parts – 3D condominiums, which are smallest parts of 3D property units in the model. Thus those, procedure of automatic valuation of spatial characteristics of each condominium were possible, instead of valuation of the whole building object. This factor was calculated as visibility polygon, two-dimensional geometric shape – cross section of continuous visibility border in all directions from one point (centre of 3D condominium), considering only the cross section of horizontal vision and obstacles. Data derived from the system can be used for better understanding and explanation of real estate value spatial distribution, and as a basis for the expert system based on multi criteria decision making.