The rapid developments in GIS such as data integration and representation, spatial data products, and new spatial data mining methods, are forcing users to deal with data of unknown or ambiguous quality; thus, unpredictable risk in decision making is inevitable. This book covers aspects of spatial data quality that have been scarcely addressed. In the era of big data, the mass volume of heterogeneous data and the proper use of the acquired geospatial data remain a significant challenge for GIS users and need to be investigated.