3D crowdsourced parametric cadastral mapping: Pathways integrating BIM/IFC, crowdsourced data and LADM

This paper is part of a doctoral dissertation (PhD) research aligned with global trends aiming to develop practical technical tools for the collection, management and visualization of three-dimensional (3D) property rights in urban areas. Recently, the Building Information Models (BIMs) claim a prominent position in the field of 3D cadastres and the digital twins of the cities. In addition to all other building information, the BIM can also provide data about the exact boundaries of all kind of legal spaces (e.g., property ownership rights as well as land use restrictions), under the support of Industry Foundation Classes (IFCs). However, the utilization of BIMs for 3D cadastral surveys is still accompanied with two main drawbacks. The first refers to BIMs limited availability, as till now they mainly encounter in new large constructions. The second refers to the complexity in defining the exact geometric location of the legal boundaries regarding the exterior/interior partitions of the construction and of the common spaces. The latter parameter is formed on the basis of the current legal legislation in each country. Through in-depth investigation of the current legal framework of each country it may be possible to visualize the various 3D legal spaces within complex constructions and thus to facilitate the integration of existing BIMs in the development of 3D cadasters that will enable a better understanding and communication of all involved parties in the operation of cross-boundary real estate markets. In parallel, crowdsourcing has already been proved to be a powerful data collection method for the initial participatory implementation of fast, reliable and affordable 3D cadastral surveys, utilizing all capabilities provided by the latest low-cost devices, mobile services (m-services), open-source software (OSS) and the international standard of Land Administration Domain Model (LADM ISO 19152). If no precise 3D building models are already available, the currently available 2D architectural plans combined with the additional geometric and descriptive cadastral information may be utilized for a participatory crowdsourced cadastral survey of the 3D property units. In this paper a ‘two-route’ crowdsourced approach is described. This approach suggests both the use of existing BIMs – those available – to proceed with 3D crowdsourced cadastral surveys of those constructions, as well as the use of 2D georeferenced basemaps (e.g., orthophotos for the compilation of 2D crowdsourced cadastral surveys, and all existing architectural floor plans of the constructions) to proceed with 3D crowdsourced cadastral surveys of all other constructions. A database schema describing the linkage between LADM standard, BIM/IFC and 3D crowdsourced geometric and descriptive cadastral information is developed and presented. A hybrid mobile application enabling the manipulation of BIM/IFC descriptive data – if existing; the collection of 3D crowdsourced geometric and descriptive information by property owners/users/non-professionals; the registration of the cadastral data and their relationships within a LADM-based cadastral geodatabase; the automated generation of 3D property unit models as block models (LoD1), using Model-driven approach; and the objects visualization in real-time, are developed. An investigation regarding the legally correct representation of the location of property unit boundaries, focusing mainly in the Greek territory is conducted. A practical experiment for each one of the cases of the ‘two-route’ crowdsourced approach is implemented, for two multi-storey buildings in the city of Athens, Greece. The potentials of the proposed crowdsourced solution as well as the achieved geometric accuracy – in the absence of BIM – are discussed and assessed. The results show that integrating BIM data with cadastral information derived from crowdsourcing, may significantly contribute to the implementation of 3D Cadastres, providing also a better visual understanding of 3D property rights. Nonetheless, even in the absence of a BIM the achieved accuracy seems to satisfy the cadastral specifications of the Greek cadaster enhancing the potential of exploiting crowdsourced data in the initial phases of the cadastral formal procedures.