This paper describes research into the design, development and visualization of mixed 2D and 3D Cadastre. A schema has been developed to accommodate this data, with provision for a time component. This paper describes the schema, the visualization requirements, and the provision of LADM-compatible views of the data for the purpose of developing the 3D Cadastral prototype. A significant volume of 2D + t Cadastral data, which also contained 2D + t footprint representations of 3D parcels, is currently incorporated in the Cadastral Database of Queensland. A moderate number of 3D building units, and a smaller number of volumetric parcels have been hand-encoded (from the survey plans), and added to this database. The mixture has been disseminated and displayed in KML through Cesium JS. The visualization of cadastral parcels in 3D is a challenge, since legal boundaries are, in many cases, invisible in the real world; so how can we properly represent something that is not visible to our eyes? This paper uses the results from research looking into problems of occlusion and ambiguous perception (in terms of position, size and shape) of objects in the context of 3D cadastre visualization. The exploration of specific interaction techniques is essential to overcome these issues. After an initial internal usability test (with colleagues/ friends of the developers) our 3D Cadastres web-based dissemination prototype was improved. Next a public usability test is carried out to obtain feedback from different groups of professional users (legal, survey, ICT backgrounds). During the test, the users are asked to perform a series of tasks typical of cadastral systems. Each task is accompanied by a description to give the users some context. Then, each user is asked to reflect on his or her experience. In this paper we present the main results of the public usability test of the 3D Cadastres web-based dissemination prototype.

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The visualization of cadastral parcels in 3D is a challenge, since legal boundaries are, in many cases, invisible in the real world; so how can we properly represent something that is not visible to our eyes? This paper uses the results from research looking into problems of occlusion and ambiguous perception (in terms of position, size and shape) of objects in the context of 3D cadastre visualization. The exploration of specific interaction techniques is essential to overcome these issues. After an initial internal usability test (with colleagues/ friends of the developers) our 3D Cadastres web-based dissemination prototype was improved. Next a public usability test is carried out to obtain feedback from different groups of professional users (legal, survey, ICT backgrounds). Usability is meant in terms of effectiveness and efficiency of the system and users' satisfaction. The test users were subdivided into groups according to different professional domains and expertise. During the test, the users are asked to perform a series of tasks typical of cadastral systems. Each task is accompanied by a description to give the users some context. Then, each user is asked to answer a questionnaire about his or her experience. The results are used to extract general feedback. The outcome of the usability test is crucial to point out the detected limitations in this early stage of the prototype development. Design changes can then be made according to the feedback of the test users. In this paper we present the main results of the public usability test of the 3D Cadastres web-based dissemination prototype.@en

Many countries are extending their cadastral visualization systems in the third dimension. The reason for this stems from the increasing complexity of contemporary cities, the growing 3D approach in other fields (including 3D spatial data acquisition, spatial data processing and visualization), which made 3D cadastre technologically feasible, and the need to overcome the issues of 2D visualization. The visualization of cadastral parcels in 3D is a challenge, since legal boundaries are, in many cases, invisible in the real world; so how can we properly represent something that is not visible to our eyes? This paper results from research that looks into problems of occlusion and ambiguous perception (in terms of position, size and shape) of objects in the context of 3D cadastre visualization. The exploration of specific interaction techniques is essential to overcome these issues. The aim of this paper is to provide ’lessons learned’ resulting from the implementation of a 3D cadastre prototype that was built with the specific goal of trying out several visualization options of 3D cadastral information in a web environment. A usability test was carried out to obtain feedback from different groups of users. Usability is meant in terms of effectiveness and efficiency of the system and users’ satisfaction. The test users were subdivided into groups according to different professional domains and expertise. During the test, the users are asked to perform a series of tasks typical of cadastral systems. Each task is accompanied by a description to give the users some context. Then, each user is asked to answer a questionnaire about his or her experience. The results are used to extract general feedback. The outcome of the usability test is crucial to point out the detected limitations in this early stage of the prototype development. Design changes can then be made according to the feedback of the test users.@en

More and more countries in the world are developing 3D Cadastre. To make cadastral information available to the potential users, both cadastral sector professionals and normal citizens, the Web can be used as dissemination platform. However, visualization of 3D cadastral information is still a challenge. Some of the main issues are: occlusion, distortion, unbounded volumes, perception of position, size and shape of an object. For orientation purposes, it is important to include reference objects to help us understand the location of the parcels in the real world. Although, the resulting higher number of objects makes the clear visualization even more challenging. We therefore first investigate the requirements to obtain a proper, clear and not misleading visualisation of 3D cadastral parcels through a geo-web viewer. We explore how to handle the above-mentioned issues such as occlusion, distortion and ambiguous perception (in terms of position, size and shape) of objects while interacting with 3D cadastre. Also, techniques for combining the visualization of legal boundaries (cadastral parcels) and real-world objects (topography) are analysed. The overall technical architecture of a system for the dissemination 3D Cadastral parcels is presented, starting with the storage of the data at the backend server (DBMS and webserver) and the possible encodings for data transfer (such as XML, JSON, glTF) to the client. WebGL based solutions at client side are preferred as these do not require the download of a plugin in the web browser, while still offering many well performing visualization and interaction options.@en

This paper describes research into the visualization of mixed 2D and 3D Cadastre. A schema has been developed to accommodate this data, with provision for a time component. This paper describes the schema, the visualization requirements, and the provision of LADMcompatible views of the data for the purpose of developing these tools, and for the further research into the schema itself. A significant volume of 2D+t Cadastral data, which also contained 2D+t representations of 3D parcels, is currently incorporated in the Cadastral Database of Queensland. A moderate number of 3D building units, and a smaller number of volumetric parcels have been hand-encoded using bespoke software, and added to this database. The mixture has been displayed in KML through Google Earth. Examples of the database schemas, the encoding practices, LADM-compatible views, and the encoded 2 and 3 dimensional spatial units are included.@en