Towards common basis for 3D Cadastres from legal perspective

Legal aspects play an increasingly important role in establishing a functional 3D Cadastre, especially in urban areas with multiple strata, crossing networks and overlapping legal spaces in the form of apartments and utility infrastructures. A wide range of national laws and regulations govern the way these real world objects and associated rights, restrictions and responsibilities (RRRs) are defined and represented in the two- or three-dimensional (2D/3D) space. In fact, despite all research and latest technological advances, no country has so far developed a real 3D Cadastre, while in all legal systems, basic terminology and key concepts need to be clarified first in order to meet the harmonisation of the different Land Administration Systems (LASs) in the near future. This paper aims to contribute to reach towards this harmonisation, by identifying similarities, differences and constraints imposed by jurisdictions that need to be addressed, to ensure 3D cadastral registration and representation of the real world objects, as well as determination of RRRs complying with the different national land law. This paper also engages in worldwide trends of modelling legal relations between spatial units and RRRs on the basis of existing standards that ensure harmonisation and interoperability. Thoughts and proposals for the integration of legally defined spaces into a 3D Cadastres system are offered, including the clarification of RRRs and related source documents, within the context of the Land Administration Domain Mode, recently approved as official International ISO Standard.