Towards an International Data Standard for Immovable Property Valuation

Immovable property valuation is performed by public sector actors for several land management activities, such as property taxation, expropriation or compulsory purchase of land, land re-adjustment and land consolidation; and private sector actors perform valuation for purchase, real estate financing, investment analysis, and further property transactions. The valuation process returns estimated value (e.g. market value) of property units based on their legal, physical, geographic, economic, and environmental characteristics, as recorded at public registries or observed on location. The ISO 19152:2012 Land Administration Domain Model (LADM) presents a conceptual schema for the specification of property units and their legal and geometric characteristics recorded at cadaster and land register, and relates these datasets with other property related datasets (e.g., valuation, taxation, land use, land cover) recorded at external databases. A recently initiated collaborative research (see Çağdaş, 2016) aims at developing a data model for one of these external databases, in terms of a Valuation Module for the ISO 19152:2012 LADM which is supposed to define semantics of valuation databases maintained by public authorities especially for immovable property taxation. The present paper presents preliminary results of this initiative, and describes a draft version of the Valuation Module which specifies the input and output data used and produced when single or mass appraisal processes are performed according to published standards and recommendations. It also presents a questionnaire which was prepared to create an inventory of valuation applications all over the world, and will be used as source data for the elaboration of the draft module. The paper also opens a discussion about this initiative, and calls for contributions of other relevant bodies (e.g. FIG, OGC, TEGOVA, IVSC and IAAO) for the further development of the draft Valuation Module.