Geoscience Reference
In-Depth Information
spatial unit for which the above is true. Hence, making the unit any larger would
result in the combination of rights not being homogenous; making the unit smaller
would result in at least 2 neighbour 3D parcels with the same combinations of rights.
A 3D parcel always refers to a “legal object” describing simultaneously a “part
of the space”. Thus, in general property cadastres there are two different types of
objects: the legal and the spatial ones. Often there is a direct relationship between
a legal and a real world spatial object. It is the spatial object that in turn may be
also described in 3D. More precisely, the focus in the context of 3D cadastres is on
3D parcels understood as “spaces of legal objects”.
Accurate collection methods of 3D spatial data are required so that relevant
data acquired at a specific time may be incorporated in a 3D data infrastructure.
Spatial data may refer to information such as on: the ownership number; the par-
cel's unique identifier; the parcel's geometric shape and area; if it is the case, on
the footprint of manmade constructions, e.g. buildings, within the parcel; build-
ing geometry; each building's floor area (Hassan and Abdul-Rahman
2010
, cited
in Abdul-Rahman et al.
2012
). As far as semantic information is concerned, this
has to be rich enough in order to provide a description about the parcel as detailed
as possible, such as: owner identity, e.g. name and national tax number; parcel
history; number of physical components; type of lease; if it is a building, number
of floors, or volume space. In 3D modelling, implicit or explicit geometry may
well be used to generate the 3D model itself. With this regard, the integration
of Building Information Models (BIM) can also help in data collection process,
though this should only be carried out if the integration of both CityGML and IFC
standards can be achieved (Abdul-Rahman et al.
2012
). The spatial unit package
defines spatial units as being 2D (land parcels) or 3D (space), buildings, or utility
networks. These include in turn topological, polygon, line, point, and text spatial
units (ISO/TC211
2012
).
2.4 An Overview of 3D Modelling Approaches
in Cadastral Systems
Further to the International Federation of Surveyors (FIG) congress in April 2002,
some work has been devoted to 3D aspects of cadastral registration systems both
in a fundamental way and at an international level. This has been done mainly in
the context of a working group set up as a joint sub-group of Commission 3 and
Commission 7 of FIG—which is in turn subdivided into three sections dealing
with the legal, institutional, and technical aspects of 3D cadastre respectively.
The joint sub-group above has promoted so far three international workshops:
Netherlands, Nov 2001 (
www.gdmc.nl/events/3dcadastres2001
); Netherlands, Nov
2011 (3dcadastres2011.nl); China, Oct 2012 (
www.cadastre2012.org
)
. A wide
range of papers have been presented throughout those workshops on 3D modelling
approaches towards what has been defined as “smart cadastre” that supports 3D
parcels (Khoo
2012
).
