Экзамен зачет учебный год 2023 / Stoter, 3D Cadastre

12.3. Conclusions

more detail.

3D physical object registration

The experiments with the case studies showed that the availability of physical objects in the cadastral geographical data set o ers better means to reflect the real situation. In addition, parcels need no longer to be divided into parcels that match the 3D objects and ‘gaps’ in the cadastral registration can easily be traced. Technical issues have to be solved to be able to maintain the complex geometry of physical objects in the cadastral DBMS. The geometries of physical objects will (mostly) have to be provided by third parties.

As can be concluded from the experiments in this case study the registration of 3D physical objects is specifically suitable for infrastructure objects, while the 3D rightvolumes are more appropriate for registering property units in building complexes.

The two concepts of the hybrid cadastre (3D right-volumes and 3D physical object registration) have a di erent line of approach and therefore meet other needs of 3D cadastral registration. The concepts could be combined to take advantages of both solutions. The disadvantage of both hybrid solutions is that the rights to real estate are still related to land and not to volumes.

Full 3D cadastre

In the full 3D cadastre volume parcels can be established that no longer have a relationship with surface parcels. This concept was applied to the Gabba Stadium case study in Queensland, Australia. The juridical framework in Queensland already provides the possibility to establish volumetric parcels as in the Gabba Stadium case, however the cadastral framework does not provide the possibility to incorporate the (precisely) defined volumetric parcels as part of the cadastral geographical data set in 3D. The prototype applied to this case study showed that is possible to use the 3D information from the 3D survey plans (needed to establish volumetric parcels) to insert the 3D geometrical and topological characteristics in the DBMS. This makes it possible to validate the volumetric parcels, to perform 3D functions on these parcels and to query and visualise the 3D situation in one integrated view containing volumetric parcels and 2.5D surfaces of standard and remainder parcels. The prototype of the full 3D cadastre showed the very good potentials of a full 3D cadastre since insight into the 3D situation is considerably improved, while the concept is based on an integrated approach of the juridical aspects (to allow volume parcels), cadastral aspects (to register volume parcels) and technical aspects (to define volume parcels in 3D survey documents and to incorporate this information in the cadastral database, followed by an integration of volume parcels and a 2.5D surface of the base map).

From the experiments with the case study in Queensland it can be concluded that, though the states and countries that already establish 3D property units have some remarkable di erences (some require real constructions to be related to the 3D property registration others not, some limit the 3D property to be within the column of one surface parcel others not, some require quite detailed 3D survey plans to support the 3D property registration others not), they all can be supported by a cadastral registration based on the proposed full 3D cadastre model, although there are some non-trivial aspects (in the conversion and use of a 3D cadastre), which require further attention.

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An important condition of the full 3D cadastre is that the juridical system is flexible enough to permit volume parcels. In other 3D cases the hybrid solution can be considered to improve traditional cadastral registration.

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Summary, conclusions and further research

The main research question of this thesis was “how to record 3D situations in cadastral registration in order to improve insight into 3D property situations”. This thesis used the cadastral registration in the Netherlands as starting point, although also cadastral registrations abroad were examined. To answer the main research question, this research was divided into four major parts. This chapter summarises these parts and lists the main conclusions that can be drawn from the four parts:

•Analysis of the background (section 13.1).

•Technical framework for modelling 2D and 3D situations (section 13.2).

•Models for a 3D cadastre (section 13.3).

•Realisation of a 3D cadastre (section 13.4).

Based on the conclusions recommendations for future directions and future research can be outlined. Section 13.5 contains recommendations for future directions towards a 3D cadastral registration in the Netherlands. Section 13.6 lists the recommendations for future research.

This chapter ends with summarising the most important results of this research.

13.1Analysis of the background

In the analysis of the background the cadastral registration of 3D property units in the Netherlands as well as abroad were studied in order to get a clear overview of the requirements, the constraints and the state-of-the-art of 3D cadastral registration. In section 13.1.1 current practise of establishing and recording rights and restrictions in 3D property situations in the cadastral registration are summarised as well as the basic limitations. Section 13.1.2 contains the juridical and cadastral constraints for a 3D cadastre that are imposed by the Dutch juridical and cadastral framework. From

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the limitations and constraints the basic needs and requirements for a 3D cadastre in the Netherlands are summarised in section 13.1.3.

13.1.1Current registration practise of 3D property units

From the survey in part I of this thesis the following conclusions can be drawn on the current status of cadastral registration in case of 3D property units.

Establishing the legal status of 3D property units in the Netherlands

In the Netherlands, property to space is related to and dependent on the property of surface parcels. Persons can only be entitled to 3D property units by establishing rights and limited rights on intersecting surface parcels. The basic drawback of the land (surface) oriented concept of property rights to real estate, is that the 3D reality in which persons are entitled to volumes is projected on the surface.

3D property units in the Dutch land registration

The deeds concerning real estate archived in the land registration (Public Registers) must always relate to land parcels. In the deeds it is possible to precisely define the space to which the concerning rights apply, for example by adding an analogue cross section. Basic drawbacks of current land registration is that 3D property units are not known as individual property units in the land registration, except in the case of apartment rights. In addition, it depends very much on the choices in the notarial deed and we may assume also on the legal advice of the notary (in the Netherlands a publicly appointed o cal charged with drawing up authentic deeds and legalising documents) how the legal status in 3D situations is established (what rights are used, are parcels subdivided) and also what information is added to the deeds. In general, there are no instructions for a 3D survey that could be added to a deed. Only in case of apartment rights an analogue drawing is obliged containing an overview of every floor (assuming that there are clearly identifiable floors) and only in case of apartment units there are special requirements concerning the quality of the spatial information. Apartment rights are also always related to one or several surface parcel(s).

3D property units in Dutch cadastral registration

The surface parcel is always the entrance to a cadastral recording. Only in the case of apartment rights individual 3D property units are known as such in the administrative part of the cadastral registration. The 2D parcel as basic (and only) real estate object in the cadastral registration meets several drawbacks. The legal status of space above and below the surface can only be obtained by collecting information on the legal status of intersecting surface parcels. However, one first has to find out which parcels intersect with the 3D construction. This is not always an easy query since the construction itself is not available in the cadastral registration. In addition, more than two million cadastral recordings were found in the cadastral database of September 2003 that could indicate a 3D situation (cases in which than more than one person has interest in the same parcel column). The third dimension of rights and restrictions of these recordings cannot be reflected in the cadastral registration, even if this information is available in deeds, drawings or survey plans. Consequently the current cadastral registration provides information on which persons have a right on a parcel but not on the spatial extent of these rights. Access to information in 3D property situations will soon be improved, since deeds and drawings archived in the

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land registration will be accessible in scanned format through the cadastral database in the near future, although this still will be limited to querying the information per parcel, instead of visualising the 3D situation of several parcels in one environment (similar as viewing the current cadastral map).

Content of the Dutch cadastral geographical data set

The cadastral geographical data set is 2D and contains parcel boundaries and buildings for reference purposes. The (footprint of) apartment units, constructions and phenomena such as soil pollution and monuments are not included in the cadastral geographical data set. Underground constructions and telecom-networks could be mapped in the topographic part of the cadastral database (which is not part of the cadastral map) by using a specific visibility and classification code. Drawback of the current cadastral geographical data set is that first of all no 3D overview can be provided of a 3D property situation. However also footprints of 3D property units are not drawn on the cadastral map. In addition, the current topographic part of LKI (September 2003) does not contain transport systems or telecom-networks (although it does contain pipelines). Consequently, the real situation is not su ciently reflected in and cannot clearly be obtained from the cadastral geographical data set.

Establishing the legal status of 3D property units abroad

The developments on 3D cadastral registration depend on the national legal system, on the type of cadastral registration as well as on the state-of-the-art of the cadastral registration (see chapter 2). The solutions abroad establishing the legal status of 3D situations use either the strict definition of ownership and property rights that is always related to surface parcels as in the Netherlands (e.g. Denmark and Israel), or are based on a more advanced concept of the right of ownership and other property rights that is no longer always related to surface parcels but can be related to volumes. The countries that use the strict definition of ownership and property rights meet basically the same drawbacks as cadastral registration in the Netherlands. The solutions that no longer relate ownership and property rights to surface parcels were found within juridical frameworks that are able (or were able after some minor adjustments) to establish multilevel ownership, e.g. ‘volumetric parcels’ in Queensland, ‘air-space parcels’ in British Columbia and ‘construction properties’ in Norway and Sweden. These solutions to establish volume parcels di er per country, e.g. the footprints of 3D property units should be within the 2D surface parcels (British Columbia) or not (Norway, Sweden, Queensland), the 3D property units have to relate to built constructions (Norway, Sweden) or not (British Columbia, Queensland), the 3D property units have to be described in survey plans (British Columbia, Queensland) or not (Norway, Sweden). From these new solutions it can be concluded that within some juridical frameworks it is possible to explicitly entitle persons to volumes, which is an important precondition for a well-working 3D cadastral registration. The establishment of 3D property units that are no longer related to surface parcels provide better means to reflect the real property situation.

3D property units in cadastral registrations abroad

Although the 3D property units can be established within the juridical framework in Queensland, British Columbia, Norway and Sweden and registered in the land registration and cadastral registration as individual property units, none of these solutions include a complete 3D cadastral registration of 3D property units. This

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causes a few problems. Firstly, a digital description of the 3D property unit in vector format is not maintained in the land registration (only scanned or paper drawings). Therefore the 3D property unit cannot be viewed interactively and the geometry of the 3D property unit cannot be validated. Secondly, the 3D properties are still not incorporated in 3D in the geographical data set of the cadastral registration (only as footprints), by which it is not possible to query and view the 3D situation in the cadastral registration. These solutions therefore do not address technical issues, such as how to store, query and visualise 3D property objects (in 3D) and how to make sure that 3D properties do not overlap (the condition that 2D parcels may not overlap assures complete and consistent registration in current cadastral registrations).

13.1.2Cadastral and juridical constraints for a 3D cadastre

Important condition of this research is that the proposed 3D cadastre has to fit to some extent within the Dutch juridical and cadastral framework and should be technologically possible. These conditions impose constraints on a 3D cadastre. The background analysis yielded insight into the cadastral and the juridical constraints as will be described in this section (the technical constraints were studied in part II: framework for modelling 2D and 3D situations, see section 13.2).

Juridical constraints

Juridical constraints, defined by the juridical framework, are dependent on the juridical doctrine and the history of the legal system in a specific country. For example in some countries the juridical framework provides the possibility to establish multilevel ownership while in other countries this is juridically impossible. The juridical constraints for a 3D cadastre in the Netherlands can be summarised as follows:

•The legal status to real estate is always established on 2D surface parcels and is (until now) land (surface) oriented.

•Right of property to a parcel is undefined in the vertical dimension (reaches as high or as low as a user has interests).

•Horizontal division of ownership is only explicitly and juridically possible by a right of superficies or an apartment right (the establishment of these rights is not accompanied with a 3D survey).

•Other limited real rights can be used to establish a factual horizontal division in ownership by describing explicit and precise limitations of the right in the concerning deed.

Cadastral constraints

Cadastral institutions, cadastral rules and cadastral instruments also lay down constraints upon cadastral registration, although the cadastral framework is more flexible (easier to adjust) than the juridical framework. For a 3D cadastre in the Netherlands, the important cadastral constraints are:

•The current cadastral geographical data set is 2D. For a 3D cadastre, the cadastral geographical data set needs to contain both 3D information on 3D property units and parcels that are draped over a height surface in one environment.

•The Dutch cadastral institution cannot enforce rules on how to register. If the information in the deed is correct, it has to be registered in the cadastral

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registration, even if there would be better possibilities to establish and register the legal status of the situation. Also requirements on the quality of the spatial information cannot be imposed, e.g. a soil pollution area on a drawing vaguely indicated by the notary is allowed. Only in the case of apartment drawings specific requirements concerning the quality and content of the drawings are imposed.

•An important question is who will finance (and organise) the 3D cadastral registration, including maintenance of the registration. This will be either the Kadaster in case the government makes the Kadaster responsible for 3D cadastral registration or the persons who benefit from the registration (e.g. holders of physical objects, but also managers and planners who query the 3D registration). Financing of a 3D registration should be supported by good organisation and legislation. In general the benefits should be larger than the costs. Also 3D registration should be cost-recovery at large.

•The cadastral registration should be connected to the Geo-Information Infrastructure (GII). In that case a 3D cadastral registration can benefit from spatial (3D) information that is maintained by other organisations and in other databases and vice versa, since information can easily be shared. Furthermore within a GII, the cadastral registration is much easier accessible for users.

13.1.3Needs and requirements for a 3D cadastre

Based on the description of current cadastral registration in case of 3D property units and the constraints of the cadastral and juridical framework in the Netherlands, the basic needs for a Dutch 3D cadastre, focusing on improving insight into 3D situations, can be summarised as follows:

•to have a complete registration of 3D rights as such (rights which entitle persons to volumes). The current cadastre already registers rights which entitle persons to volumes, e.g. full ownership (applies to whole parcel column), right of superficies etc., however a 3D cadastre should explicitly register the space to which rights apply;

•to have good accessibility on the legal status of 3D property units including (3D) spatial information as well as on Public Law restrictions.

It will be more e ective (e.g. with respect to data integrity and data consistency) if information on constructions and other objects of interest is maintained at their source (e.g. in databases of holders of constructions) and accessible within and from the 3D cadastre within a GII.

Based on these considerations, we can conclude that a 3D cadastre should incorporate the following functionalities:

•register 3D information on rights (what is the space to which the person is entitled?) and make this information available in a straightforward way;

•establish and manage a link with external databases that contain objects that are of interest for the cadastre (infrastructure objects, soil pollution areas, forest protection zones);

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•use the information on these objects to support registration tasks, i.e. to detect and correct errors in cadastral registration or in the process of registering and viewing the legal status of 3D property. Are all intersecting parcels encumbered with a right for the infrastructure object?

13.2Framework for modelling 2D and 3D situations

The 3D cadastre needs to be implemented using current and new techniques. The framework of modelling 2D and 3D situations was studied in part II of this thesis. In chapter 6 it was concluded that DBMS plays an important role in the new generation GIS architecture. Consequently to implement the 3D cadastre, in which a lot of information needs to be managed, a DBMS is needed for maintaining the cadastral (spatial and non-spatial) information concerning 3D situations.

Fitting this research in a technical framework required a study to what is technically possible with respect to maintaining, accessing and analysing 3D geo-information in DBMSs using standard products and additional developments. Current technologies were tested and concepts were designed and implemented into prototypes to improve current technology.

In section 13.2.1 the conclusions on possibilities of support of spatial data types in geo-DBMSs are drawn. Apart from geo-DBMS other developments of 3D GIS are important for the 3D cadastre research, since available 3D GIS functionalities in general impose constraints and provide possibilities on how to maintain, access and analyse 3D geo-information. In section 13.2.2 the state-of-the-art of 3D GIS is summarised. How to access spatial information stored in a DBMS with di erent front-ends (as the new generation GIS architecture is organised) is described in section 13.2.3. Finally, in section 13.2.4 the possibilities and problems of combining 2D and 3D geo-objects in one environment are described.

13.2.12D and 3D geo-objects in geo-DBMS

The 3D spatial component of constructions and rights, but also of parcels, has to be registered in the cadastral database. This raises the question how to structure spatial objects in 2D and 3D in a DBMS. Concerning this, the following conclusions can be drawn.

2D and 3D geometrical primitives in DBMS

Geometrical primitives as defined by the OpenGIS Consortium (OGC) have been adapted by mainstream DBMSs and popular non-commercial DBMSs. The OpenGIS Implementation Specification for SQL [148], is until now 2D. It also does not cover topological structure, although topological relationships can be obtained by spatial functions on the geometrical primitives. The ISO DIS 19107 standard [87] (adopted as Abstract Specification by OGC) does define 3D spatial objects and topological structure, however these Abstract Specifications still have to be transformed into Implementation Specifications by OGC and to be adopted by DBMSs.

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13.2. Framework for modelling 2D and 3D situations

Current DBMSs do not support 3D volumetric data types. To maintain 3D geometrically structured data within current techniques, 2D primitives defined in 3D embedding space can be used (polygon defined in 3D). 3D objects can be defined either as a body that consists of a set of faces or as a multipolygon defined in 3D. However, these 3D objects are not recognised as such by DBMSs or only in a limited way (e.g. to calculate the 3D length of a line). The z-coordinates are stored while in nearly all spatial analyses and validation checks the 3D object is projected on the surface. To support true 3D in a DBMS, a 3D geometrical primitive (polyhedron) has been defined and implemented in the DBMS as part of this research. Using this primitive 3D geometries can be defined consisting of flat faces including holes. This implementation shows the possibilities of maintaining 3D objects in a geometrical structure. As part of the implementation 3D spatial functions and a 3D validation function were implemented.

2D and 3D topological structures in the DBMS

Awaiting an Implementation Specification for 2D (and 3D) topological structure, there are already some user-defined (section 7.2.2) and commercial implementations of 2D topological structures available (Laser-Scan, see section 7.2.3, and Oracle 10g). These implementations look promising when applying topological queries on the structures (good performance). However geometrical queries are faster on the geometrical primitives since many tables need to be queried to get a geometrical realisation of the topological structure before the geometrical query can be executed. At the moment topological structure is therefore mainly appropriate for representing relationship operations and for checking the quality of the data. The topology structure o ers better maintenance possibilities with respect to quality. Topological structure supports consistency of spatial data since shared lower-dimensional objects are stored only once, in contrast to data defined with geometrical primitives. Topological structure management to maintain 3D geo-objects and 2D geo-objects for the 3D cadastre is preferred, but, as can be concluded from this thesis, has to be implemented using self-defined extensions.

We experimented with a DBMS implementation of a 3D topological structure: SSM (Simplified Spatial Model) which is a topological structure described in [240]. This topological structure only supports flat faces (as the implemented polyhedron primitive). In an object relational DBMS, the relationships between the high-dimensional (3D body) and low-dimensional objects (FACE and NODE) can be stored. The implementation shows that storing a 3D object and generating a geometrical realisation of the 3D object within the DBMS is not a problem. However since the topological structure is not recognised by the DBMS, topological consistency has to be checked and guaranteed outside the DBMS, available spatial indexing cannot be used and spatial functions have to be self-defined (intersection, distance).

Summarising, the 2D geometrical primitive (including spatial operations) is well implemented in DBMSs, support for topological structure in 2D in DBMSs just started but will most probably be available in DBMSs within a few years, while none of the DBMSs have started with support for 3D volumetric objects (either using geometrical primitives or topological structure). Also the OpenGIS Consortium still has to decide on Implementation Specifications for a geometrical and a topological schema in 3D. Therefore the 3D cadastre will have to be based on a combination of commercial

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products and user-defined extensions which showed potentials in the experiments in this research.

13.2.23D GIS

In chapter 8 an extended overview was given concerning other basic aspects (apart from DBMS aspects) of 3D GIS: organisation of 3D data, 3D data collection and object reconstruction, visualisation and navigation in 3D environments and 3D analysing and 3D editing. Based on this overview it can be concluded that 3D GIS still has to mature. 3D GIS developments are mainly in the area of visualisation and animation. Bottlenecks for commercial implementation of 3D GIS are:

•3D editing in GIS is not (yet) possible and is traditionally a functionality that is well supported in CAD software but not in GIS;

•poor linkage between CAD, traditionally designers of 3D models, and GIS;

•lack of methods to automatically reconstruct 3D objects;

•visualisation of 3D information requires special techniques; characteristics such as physical properties of objects (texture, material, colour), behaviour (e.g. on- click-open) and di erent levels of detail representations need to be maintained and organised in DBMSs;

•Virtual Reality and Augmented Reality techniques should be incorporated in GIS software to improve interaction with and visualisation of 3D environments.

13.2.3Accessing spatial information organised in a DBMS

Once 3D geo-objects are stored in a DBMS within current techniques, the next issue is how to access and query the geo-objects by front-ends. Three front-ends were analysed to access 3D objects stored in (3D) geometrical primitives in Oracle Spatial 9i: a CAD oriented front-end, a GIS front-end and a self-developed front-end using Web based techniques.

CAD oriented front-end

With the CAD oriented software MicroStation GeoGraphics (MS GG) it is rather easy to visualise 3D objects stored as multipolygons in a DBMS, however querying and editing 3D objects require more complex steps but it is possible while true 3D editing is supported in MS GG. The main disadvantage is that the database structure is altered. The Java applet ‘Spatial Viewer’ that is delivered with MicroStation GeoGraphics requires less customisation and is therefore easier to use.

GIS oriented front-end

To be able to access a spatial layer stored in Oracle Spatial with the GIS front-end ‘ArcGIS’, one first needs to register the spatial layer with ArcSDE. After registering the spatial layer, querying of spatial objects is, apart from some small problems, straightforward and the tables structure is not altered. One major complexity of ESRI is that ArcSDE validates spatial objects before they are inserted into ArcGIS. This means that spatial layers containing invalid spatial objects cause problems. The main consequence of not being able to handle invalid objects, is that ‘vertical’ polygons

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