Open geodata : definitions and quality assessment of some datasets in Italy

The diffusion and the availability of Open Data has considerably increased over the last decade. Thanks to their open license, they have become fundamental tools for spreading different kinds of information which are easily accessible to anyone. Among all the available types of Open Data, this thesis focuses on the evaluation of open geospatial products (named open geodata), i.e. datasets characterized by geographical information. The importance of this Open Data was demonstrated in many studies, which showed e.g. that spatial data products have the highest commercial value of re-use as they can be involved in many different sectors, and that a business growth of 15% was found in countries where spatial products are open. Hence, over time open geodata have become more and more important in many disparate fields and even in the daily life. The work investigates whether the current situation of open geodata in the area of the Metropolitan City of Milan follows the worldwide tendency of general increase of open data. Another important informationinvestigated in this work is the spatial data quality, the most relevant aspect after the open data availability. Low quality datasets are harmful, as they may spread wrong information. For this reason, experts and producers have been studying spatial data quality since 1970 and the subject is still relevant. Thus, the objective of the thesis is to solve two different issues for the Metropolitan City of Milan: the analysis of the availability of open geodata and the evaluation of their quality. For the latter aspect, beside the general methodology, two relevant examples of quality assessment are provided. The thesis is divided in 4 Chapters. Chapter 1 is an overview on Open Data, with a particular focus on open geodata and their quality. Chapter 2 explores and catalogues the available open data for the Metropolitan City of Milan, adding detailed information on geodata. Chapters 3 and 4 propose the quality assessment of two open geodata, following two different procedures. Chapter 3 assesses the positional accuracy of an orthophoto following specific international guidelines, while Chapter 4 assesses the positional and semantic accuracy of a Land Use map through comparison against a chosen reference dataset.