DOES COIMBRA NEED A 3D CADASTRE? PROTOTYPING A CROWDSOURCING APP AS A FIRST STEP TO FINDING OUT

Abstract. The Municipality of Coimbra in Portugal, and indeed the country as a whole, is currently undergoing a long-term land registration (cadastre creation) exercise, with approximately 50 % of the country having been surveyed, amounting to 1/3 of the total properties, by the end of 2013. The survey process is currently generating two-dimensional (2D) maps. However, as with many other countries, these maps have limitations when representing the real three-dimensional (3D) complexities of land and property ownership. Capturing 2D cadastre is an expensive process, and does not provide the required insight into the number of properties where the ownership situation is inadequately represented, as the survey does not include the internal building structure. Having information about the extent of the 2D/3D issue is, however, fundamental to making a decision as to whether to invest resources in even more expensive 3D survey.

Given that the 3D complexity inside buildings is only known to residents/occupants - thus making crowd sourcing perhaps the only economically feasible approach for its capture - this paper describes the development of a web-based App envisaged for use by the general public to flag different land and property ownership situations. The paper focuses on two aspects of the problem - firstly, identifying an appropriate, clear, set of diagrams depicting the various different ownership situations from which the user can then pick one, and secondly prototyping and user testing an App for multi-platform VGI data capture in absence of direct feedback from the final end users - i.e. the general public.