Investigating 3D spatial unit's as basis for refined 3D spatial profiles in the context of LADM revision

Dense urbanisation has led to an increasing demand and pressure for land development, resulting in the partition of 3D space into different owners sharing delimited property interests on, above or below the land surface. Consequently, cadastral spatial units range from simple, but most common, 2D, to complex 3D collections of spaces worldwide, that are more difficult to handle in terms of surveying, storing in a database, maintaining, visualising, etc. Subsequently, this asks for the categorization and organization of the different types of spatial units that are physically identified and legally recognised in various jurisdictions worldwide. In the context of the Land Administration Domain Model (LADM) (ISO 19152, 2012), the “level” concept (LA_Level class) provides a framework for organising the different types of spatial units. Based on that, five levels of encoding are defined in ISO19152, providing a framework of categorisation of 2D spatial units, represented by five spatial profiles included in Annex E of ISO 19152.
Six years after the publication of the first edition of LADM as ISO standard, a lot of research has been carried out by experts from all over the world, and today, the ground seems to be mature for the LADM (edition I) revision, which started in May 2018, as a joint activity with many stakeholders involved (ISO TC211, OGC, FIG, etc.). One of the goals of the revision, among others, is to improve LADM’s current 3D support. This can be achieved through the design of new 3D spatial profiles for the different types of spatial units that are recognised by cadastral authorities in various jurisdictions. New and different 3D spatial units’ types may be considered for inclusion in the standard.
To this end, the aim of this paper is to investigate, examine and review - in the context of LADM revision- the different types of real-world spatial units, as they have initially been organised by Thompson et al (2015). Based on the revised taxonomy, spatial profiles for the spatial units’ categories are introduced and (several) are further explored and designed. Hence, the focus on this paper lies on two levels: the taxonomy and the spatial profiles, while the level of encoding is not included in the scope of this paper. However, the investigation of the technical encodings that will be used for the implementation of the 3D spatial profiles is introduced at the paper as future work, underlying its importance. Within this concept, the scope and ambition of LADM revision are discussed.