Creating and analysing a constrained TIN in a geo-DBMS: integration of point heights and parcel boundaries

In a study concerning 3-D cadastre ( Stoter et al., 2002 ) a prototype has been built that provides insight on the vertical dimension of rights registered in the cadastral registration system. This is important when different properties are located above each other (such as tunnels, pipelines and building complexes). In the prototype, parcel boundaries need to be located in 3-D space as they have to be combined with 3-D objects such as tunnels and pipelines. To extend the spatial model of parcel boundaries into 3-D, simply assigning one z-coordinate to each parcel is not sufficient. Providing a z-coordinate to the vertices describing parcel boundaries also does not meet the requirements for a 3-D cadastre. In this paper we elaborate on how parcel boundaries can be integrated with point heights to meet the requirements for a 3-D cadastre; i.e., obtaining a height surface for parcels. A height surface for parcels is the digital terrain model (DTM) on the locations of parcels. A parcel surface changes when the terrain surface changes. We will describe and evaluate several possibilities for obtaining a height surface for parcels based on a DBMS approach.