Conversion of 2D analogue cadastral boundary plans into 3D digital information - problems and challenges illustrated by a Swedish case

The possibility of forming 3D property units has not existed for a long time in Sweden. The legislation was introduced in 2004 and in 2009 the addition of apartment ownership (condominium) was added. Even though the demand for 3D property formation has not been as high yet as initially expected, there seems to be an increased interest in and demand for it today. The use of 3D property creates a need for 3D registration and visualization of the property units, which can involve difficulties in e.g. representation and storage of 3D real property data, such as the legal boundaries and real property rights connected to the property.
However, even if 3D digital information is used in the real property formation process the 3D properties are still registered using two–dimensional documentation. An ongoing study, which is a part of a project testing 3D data, see Andree et al. (2018a; 2018b) and Tarandi (2017), is focusing on visualization of 3D cadastral boundaries.
This paper discusses problems and challenges concerning the conversion of 2D analogue cadastral boundary plans into 3D digital information and is based on experiences being gained in a research project on visualization of 3D property boundaries in Sweden, see Andree et al. (2018a; 2018b). A newly constructed sports– and event arena in Stockholm where 3D properties are involved is used as a case study in the project to illustrate the process and the problems related to it. Focus lies here on legal issues, although other aspects will be mentioned as well.
The legal foundations for 3D property formation in Sweden are primarily the Swedish Land Code (SFS, 1970:944) and the Real Property Formation Act (SFS, 1970:988). The rights, restrictions and responsibilities, RRRs, are registered in the national Real Property Register, which also includes registration in the two–dimensional digital cadastral index map.
A description of the process of forming 3D property is included in the paper regarding the documents and parties involved. In the present cadastral processes concerning new 3D property formation a CAD drawing containing 3D real property boundaries is often supplied by the developer/entrepreneur. However, the 3D cadastral representation and the documentation in the cadastral dossier is recorded in 2D (El–Mekawy, Paasch and Paulsson, 2014). The CAD file may – or may not - be archived for future use by the Cadastral authority. We therefore sometimes may have to interpret two–dimensional data and convert it to be used in a 3D environment, e.g. BIM. This paper illustrates and exemplifies with some experiences of interpreting the cadastral dossiers for presentation in a 3D digital environment.
Current legislation has to be investigated and interpreted to be able to add or transform into using 3D models as part of cadastral decisions in Sweden. New regulations also may have to be introduced and analysed. In this paper some of the legal issues that need to be addressed are mentioned, however more work needs to be done in order to get answers to what changes may be needed regarding legislation on this matter.