This paper refers to the creation or update, organisation and initial analysis of the results from the 4th FIG 3D Land Administration Questionnaire, as an activity of the FIG Working Group 3D Land Administration 2022-2026. The questionnaire on 3D Land Administration is conducted as a successor of the previous questionnaire on 3D Cadastres, which has been conducted three times till today, by the Working Group in 2010, 2014 and 2018. The first, documented the status in 2010 and expectations back then for 2014. This was followed by the second questionnaire (status 2014 and expectations 2018) and the third one (status of 2018 and plans for 2022). All members/ countries the Working Group have been requested to provide information about the current the status of 3D Land Administration Systems/ Cadastres (at the end of 2022) and the expectations/plans for 2026. The purpose of the survey that is has been conducted and reported in this paper, is to make an inventory of the status of 3D Land Administration at the end of 2022 and the plans/ expectations for the near future (2026) from countries all over the world. The completed questionnaires, per country are fully available via the participants’ page of the 3D Land Administration Working Group website. The responses have been analysed and reported in various publications (van Oosterom et al. 2011, van Oosterom et al. 2014 and Shnaidman et al., 2019). In total, thirty-seven (37) countries have completed the questionnaire and have been received by time of conducting the initial analysis as described in this paper. Similar to the previous questionnaires, it is likely that there will be some completed questionnaires that will be sent by the countries later. @en

Subdivision of land parcels in the vertical space has made it necessary for cadastral jurisdictions to manage cadastral objects both in 2D as well as 3D. Modern sensor and hardware capabilities for capture and utilisation of large point clouds is one of the major drivers to consider Spatial Database Management Systems (SDBMS) in 3D and organisations are still progressing towards it. 3D data models and their topological relationships are two of the important parts of 3D spatial data management. 3D spatial systems should enable data models that handle a large variety of 3D objects, perform automated data quality checks, search and analysis, rapid data dissemination, 3D rendering and visualisation with close linkages to standards. This chapter asserts that while there has been work done in defining 2D and 3D vector geometry in standards, it is still not sufficient for 3D cadastre purposes as 3D cadastral objects have a much more rigorous definition. The Land Administration Domain Model (LADM), which is an ISO Standard, addresses many of the issues in 3D representation and storage of 3D data in a database management system (DBMS). The chapter further discusses the various approaches to storing 3D data such as through voxels, or point cloud data type and elaborates on the characteristics of a 3D DBMS capable of storing 3D data. Approaches for spatial indexing to improve the fast access of data and the various available options for a 3D geographical database system are presented. Several spatial operations on and amongst 3D objects are illustrated with linkages to the current standards including the LADM. Next, construction of 3D topological and geometrical models based on standards and including their characteristics is discussed. Current 3D spatial database managements systems and their characteristics, including some comparison between selected DBMS including the hardware capabilities are elaborated in detail. Finally, the chapter proposes a 3D topology model based on Tetrahedron Network (TEN) synchronised with LADM specifications for 3D cadastral registration. This topological model utilises surveying boundaries to generate 3D cadastral objects with consistent topology and rapid query and management capabilities. The definition for validation of 3D solids also considers the automatic repair of invalid solids. Point cloud and TEN related data structures available in SDBMSs are also investigated to enable storage of non-spatial attributes so that database updates would store all spatial and attribute information directly inside the spatial database.@en

Cadastral databases have unique requirements not shared by other spatial databases: The third spatial dimension must be included, but visualisation using 2D software must also be accommodated. The majority of users of the Cadastre will use 2D software, and should be provided an “instant in time” plan view of the boundaries (with any 3D parcels “flattened”). Some users will have access to and need for fully functioned 3D software, and some to tools with “time sliders” but access to the Cadastre cannot be restricted to such users. A history of the Cadastre must be maintained. It is important that patterns of subdivision and land use can be tracked through the past, and it is highly desirable that planned future activity is included. In addition, a record of the state of knowledge of the database is needed (in case past decisions must be reviewed). That is to say, both the “valid time” and “transaction time” forms of time stamping needs to be accommodated. The accuracy of the data is constantly being improved (each time a new survey is done), and this action must be reflected within the database as it becomes available. Other parties traditionally use the Cadastral database as a “base map”, and accuracy improvements need to be promulgated to these parties. This paper builds on previous research and development – mixing 2D and 3D cadastre has already been demonstrated, as has Cadastre with transaction time history. This paper considers what is needed to complete the schema. Specifically: The storage of real-world (valid time) history. The storage of “tentative time” temporal data for proposed developments. Database (transaction) time, supported by versioning. The improvement of accuracy of Cadastral boundaries, both in 2D and 3D spatial units, and of historic spatial units. 2D and 3D views of the data, and 2D update of the data. Making the data available in scalable services, including access to historic items, and update history. The novelty of this research is the combination of the full 4D/5D functionality in a single schema that can be implemented in a practical multi-user Cadastral database. This is the first time such a rigorous solution has been presented.@en

The 3rd FIG 3D-Cadastres Questionnaire was conducted and distributed by the end of 2018, with an extended deadline of 15th of January 2019. The questionnaire survey is a part of the FIG working group 3D-Cadastres activities for the period of 2018-2022. The purpose of this survey is to prepare a comprehensive inventory of the current (2018) state of 3D Cadastres worldwide, to explore the near future (2022) plans and expectations in the field and to evaluate the progress during the past four years. Sharing and dissemination of this information, enable to improve cooperation, to learn from each other and to support future developments as well as to encourage collaboration between various countries and jurisdictions. As can be determined from the title, this is the third time that the questionnaire on 3D-Cadastres is being carried out. The first version was administered in 2010 in order to document the status of 2010 3D Cadastres and of the then upcoming 2014 expectations. This was followed by a second questionnaire in 2014 (with status of 2014 and ambitions for 2018). The previous responses (van Oosterom et al., 2011; van Oosterom et al., 2014) were analyzed and reported at earlier FIG events (Working Weeks and workshops). The structure of the 3rd questionnaire has remained rather similar. All of the sections and the numbering of the questions were preserved to allow straightforward comparison with the earlier questionnaires and identification of potential trends. A few questions have been refined for clarification and several new questions have been added at the end of the sections. In this paper the main results of the analysis of the submitted 2018-2022 questionnaire are presented together with an analogy drawn between the past and present responses.@en