Web-based visualization of 3D cadastre

Abstract

Many countries in the world are extending their cadastral visualization systems in the third dimension. The reason of 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 huge challenge, since legal boundaries are, in some cases, invisible in the real world. Several countries built their own 3D cadastre (partial) systems/prototypes which are still lacking some crucial functionalities, therefore this research will try to fill some of the gaps of the existing cadastral systems with a special focus on visualization and dissemination aspects.
The goal of this research is to solve issues of occlusion, representation of unbounded vol- umes and ambiguous perception (in terms of position, size and shape) of objects in the con- text of 3D cadastre visualization. Additionally, the combination of topography and cadastral parcels is a double-edged sword; on one hand, it is useful for orientation purposes but, on the other hand, the growing complexity and increasing occlusion can make the visualization more challenging. The exploration of specific interaction techniques is fundamental to over- come these issues.
This document provides guidance on the system design choices to implement a 3D cadas- tre prototype. The study starts with a theoretical and a technological research carried out to investigate the state of the art in 3D cadastre visualization and to explore the existing WebGL platforms on which to build a successful prototype. Along with these phases, two lists of requirements are created; the first one related to 3D visualization issues and the second one related to the web viewer functionalities. The implementation of the prototype is carried out following (part of) the requirements listed, leaving the rest for future work. The development phase is the core of the research and includes the selection of the datasets and of the area of interest located in the city centre of Brisbane, Australia. In addition to that, the definition of the LADM compliant storage schema and the process of data encoding, to transform the data from survey plans to a cadastral database, are described. Although these steps are not in the main scope, they are crucial for the development of the prototype. After that, different visualization functionalities have been implemented, each of them presenting drawbacks and difficulties mainly related to the data format chosen.
In order to assess the usability and user-friendliness of the 3D cadastre prototype, a ques- tionnaire has been handed out to potential users of the application. Their feedback is funda- mental for this research and will provide insights on how to improve the actual design of the prototype.