Technical aspects for 3D hybrid cadastral model

Abstract

Urbanisation and increasing use of space above and below land surface with a fragmented tenure status brings the need for transforming existing cadastral systems based on a two-dimensional parcel representation of space (2D cadastral unit), into three-dimensional cadastral systems. The recent technological developments provide the necessary tools such as spatial databases, 3D GIS and CAD applications that may be effectively used for 3D modelling, spatial analysis and visualisation of 3D cadastral objects. This paper proposes a smooth transition from the existing 2D GIS national cadastral systems to a 3D hybrid model, so as to preserve the existing 2D unit systems but also integrate 3D representations of the physical objects. Three alternative approaches for the development of the 3D cadastral system are developed and presented. In the first two approaches the cadastral registration of objects is implemented in the SDBMS of Oracle Spatial, which is linked to a Geographic Information System (ArcInfo) and AutoCAD Map 3D respectively, so that the properties are visualised in three-dimensional level. In the third approach, the registration and 3D representation of cadastral objects are implemented in the ArcGIS environment, while for their 3D modelling Google SketchUP is chosen, because of its capability to incorporate 3D models to ArcGIS. An application of a 3D cadastral process is developed for the island of Kimolos, Greece, in which typical examples of special real property objects exist, such as settlements carved into the rocks with overlapping projections of the private properties, and/or settlements with buildings arching over the alleys with overlapping projections of the private and public properties. The results of the implementation of the three approaches are given, regarding the advantages and weaknesses of each approach through appropriate comparisons. Finally a proposal for the best procedure for creating a 3D hybrid cadastral model is given.