Ed. note: This article is Peter van Oosterom's introduction to the 2nd International Workshop on 3D Cadastres, which takes place Nov. 16-18 in Delft, The Netherlands.
In the past decade various activities have been conducted related to 3D cadastres. International awareness of this topic began with the first workshop on 3D cadastres, held at Delft University of Technology in 2001. The workshop was held under the auspices of the International Federation of Surveyors (FIG), specifically under commission three - Spatial Information Management - and commission seven - Cadastre and Land Management. This was followed by a session at every FIG working week and congress afterward. The Second International Workshop on 3D Cadastre is now being organized as a joint activity of the FIG (again, under commissions three and seven), the European Spatial Data Research Organization (EuroSDR) and Delft University of Technology.
During the past decade the on-going developments at cadastral organizations in many countries provided better 3D support. The increasing complexity of infrastructure and densely built-up areas has necessitated proper registration of the legal status (private and public), which is provided only to a limited extent by the existing 2D cadastral registries. Despite all the progress and research in place, no country in the world has a true 3D cadastre. The functionality is always limited in some manner - for example, only registering volumetric parcels in the public registers, but not in a 3D cadastral map, or limited to a specific type of object with ad hoc semi-3D solutions, such as buildings or infrastructure. At the FIG Congress in April 2010 in Sydney a working group on 3D cadastres was formed in order to make further progress. The registration of the legal status in complex 3D situations is investigated under the header of 3D cadastres. The 3D cadastre working group 2010-2014 has as its starting point the observation that an increasing amount of information is required on rights, use and value in complex spatial and/or legal situations. The main objective of the working group is to establish an operational framework for 3D cadastres. The operational aspect addresses the following requirements:
- A common understanding of the terms and issues involved. After the initial misunderstandings in the early days (due to lack of shared concepts and terminology), the concepts should now be further refined and agreed on, based on the ISO 19152 Land Administration Domain Model (LADM, which provides support for 3D representations).
- A description of issues that have to be considered (and to what level) before determining what form of 3D cadastres can be implemented, a checklist of sorts for the implementation of 3D cadastres. This will provide “best practices” for the legal, institutional and technical aspects. These findings will be translated into basic guidelines for the implementation of 3D cadastres.
The main purpose of this workshop is to have a fruitful exchange of ideas. There is no single, best solution for a 3D cadastre. In all cases for the establishment of such a cadastre, legal, institutional and technical issues have to be addressed. The level of sophistication of each 3D cadastre will, in the end, be based on the user needs, land market requirements, legal framework and technical possibilities. Therefore, in line with the ISO 19152 Land Administration Domain Model (LADM), the optimal trade-offs between 2D and 3D cadastral solutions will be explored.
It is also imperative to address the issues that arise in the transition zones between 2D and 3D representations. The concept of 3D cadastres with 3D parcels is described in the broadest possible sense. 3D parcels include land and water spaces, both above and below surface. However, what exactly a 3D parcel is (or could be) is dependent on the legal and organizational context in the specific country (state, province). For example, in one country, a 3D parcel related to an apartment unit is associated with an ownership right, while in another country the government may be owner of the whole apartment complex and the same apartment unit relates only to a use right. In both cases there are explicit 3D parcels, but with different rights attached. A third country may decide not to represent the apartment units with explicit 3D geometries at all (and the 3D aspect is then just conceptual).
A more formal definition: A 3D parcel is defined as the spatial unit against which (one or more) unique and homogeneous rights (e.g. ownership right or land use right), responsibilities or restrictions (RRRs) are associated with the whole entity, as included in a land administration system. Homogeneous means that the same combination of rights applies equally within the whole 3D spatial unit. Unique means that this is the largest spatial unit for which this is true. Making the unit any larger would result in the combination of rights not being homogenous. Making the unit smaller would result in at least two neighboring 3D parcels with the same combination of rights.
There are several 3D cadastre scope options, which need to be investigated in more detail, and the result will define the scope of the future 3D cadastres in a specific country:
- What are the types of 3D cadastral objects that need to be registered? Are these always related to (future) constructions (buildings, pipelines, tunnels, etc.), as in Norway and Sweden, or could they be any part of the 3D space, either airspace or in the subsurface, as in Queensland, Australia?
- In case of (subsurface) infrastructure objects, such as long tunnels (for roads, metro, trains), pipelines, cables: should these be divided based on the surface parcels, as in Queensland, Australia, or treated as one cadastral object, as in Sweden? I
- For the representation (and initial registration) of a 3D cadastral object, is the legal space specified by its own coordinates in a shared reference system (as is the practice for 2D in most countries) or is it specified by referencing existing topographic objects/boundaries (as in the British style of a cadastre)?
Note that there can be a difference between the 3D ownership space and the 3D restriction space; for example, one can be owner up to ±100 m around the earth surface, but only allowed to build from -10 to +40 m. Both result in 3D parcels, that is, 3D spatial units with RRRs attached. The ownership spaces (parcels) should not overlap other ownership parcels, but they are allowed to overlap other space, for example, restriction parcels.
The organization of this workshop was supported by the Open Geospatial Consortium (OGC), International Society for Photogrammetry and Remote Sensing (ISPRS) and Geo-informatie Nederland (GIN) by endorsing the workshop within their communities. The sponsors, Oracle, Bentley, Esri, Kadaster and Netherlands Geodetic Commission, part of the Royal Netherlands Academy of Arts and Sciences (NCG-KNAW), are gratefully acknowledged for their financial contributions, lowering the threshold for other participants, but in many cases also for their content contribution in the form of a paper in the proceedings and presentations at the workshop. The call for workshop contributions included the following list of relevant topics:
- Analysis of 3D use cases
- 3D legal objects and physical objects
- Building units (apartments) as 3D parcels
- 3D constructions as 3D parcels
- Utility networks as 3D parcels
- Airspace or subsurface space 3D parcels
- Potentially unbounded 3D parcels (toward the sky)
- Natural resources (groundwater, mining) as 3D parcels
- Polluted areas as 3D parcels
- Spatial (zoning) plans as 3D parcels
- Legal framework for 3D cadastre
- Range of RRR (rights, restrictions, responsibilities) attached to 3D parcels
- 3D data acquisition (survey plans)
- Initial registration of 3D parcels
- 3D data management
- 3D cadastres and models
- Relationship 2D and 3D parcels
- Height representation: absolute/relative
- 3D geometry and topology
- 3D cadastres and time
- Implementation in a cadastral database
- Visualization, distribution and delivery of 3D parcels
- 3D exchange formats
- Web-based access to 3D parcels
- 3D cadastres and spatial information infrastructure
- 3D cadastres and usability
In total, the call for contributions resulted in 38 abstract submissions covering most of the topics mentioned above. Each abstract was typically reviewed by three or four PC-members. Based on the (very) good review scores, 32 contributions were selected and their authors submitted full papers to the workshop. These are all included in the proceedings, both on paper (in black and white) and online (with color). The workshop has two types of sessions: plenary presentation and discussion sessions (typically a 20-minute presentation and 10-minute discussion per contribution), and parallel work sessions (two 90-minutes sessions in four groups). The proceedings of the workshop also contain the four position papers of the work session chairs.