Geoscience Reference
In-Depth Information
3D cadastre, nevertheless legislation and institutional are still significantly impor-
tant and need to be paid more attention. Portugal cannot currently embark in a full
nationwide 3D cadastre for this is not supported yet by the country's cadastral leg-
islation; even so, for the time being a full 3D cadastral law was assumed for the
investigation on implementation purposes.
Finally, although the complexity of each system largely depends on legal
and institutional circumstances, technological approaches available, and users'
demand, discussion and research on 3D cadastre should be accomplished from an
international perspective, as it would provide global experience and guidelines in
order to facilitate the development process (FIG
1995
). Although Portugal's con-
text is in fact the ultimate aim of our research, our case studies hereby presented
were sought and discussed from the international perspective above namely fore-
seeing possible similar instances across the world.
4.2 Issues and Recommendations
Preliminary implementation tests revealed three major issues. Firstly, geospatial
data used in our case studies are not fully adequate for 3D cadastre purposes;
in fact, 2D data were mostly used and third dimension data were derived from
other sources of data. Secondly, each national/federal/state's cadastral legis-
lation must reflect 3D situations upon which any conceptual modelling should
be based; as stated above, a full 3D cadastral law was assumed in our case for
investigation purposes and hence our prototype model does not fully match cur-
rent Portuguese cadastral legislation as it stands. Thirdly, our approach does
not cover the concept of both “airspace” and “subterranean” blocks. As to this
aspect, a fifth and a sixth entities should have been possibly considered and
added to Table
1
; indeed, as well as BUILDING entities, an airspace block or
subterranean block may well be made of one or more PART-GEOMETRY
entities.
Further to our preliminary case study implementation tests, it should be empa-
thised that accurate collection methods of 3D spatial data are absolutely required
so that relevant data acquired at a specific time may be incorporated in a 3D data
infrastructure. In addition, both legal and institutional aspects should be studied
together alongside with technical aspects. Furthermore, the modelling and descrip-
tion of the entire 3D space with no gaps is needed for the full achievement of a
3D modelling approach. This idea may well be seen as an extension of the equiva-
lent concept in 2D polygon contiguity topology where neither gaps nor overlaps
are allowed; thus, besides manmade infrastructures, other physical spaces have to
be considered, namely airspace and subterranean 3D blocks. As a general recom-
mendation, we shall say then that any conceptual model should take into account
physical spaces as well as legal/institutional spaces. As far as physical spaces are
concerned, we hereby propose irrespectively of the country the consideration of
namely:
