Spatial analysis is a core aspect of GIS for decision-making processes. The terms spatial analysis and geoprocessing are sometimes interchangeable, since some geoprocessing outputs offer decision support to geospatial information users. In fact, spatial analysis is dependent on your own imagination, and GIS provides a tool set to achieve your goal. Most spatial analysis is based on mathematics and statistical methods with geographical positions. For example, the mean value in statistics will become the mean centre in GIS. Moreover, graph theory can greatly contribute to spatial analysis via concepts such as union, intersect, network analysis, Voronoi diagrams, etc. 3D visualisation can improve the visibility of your spatial data in a way that feels like a real-world situation. Many spatial analysis functions are available from third-party developers as plugins in QGIS. In this section, we will discuss the 3D raster (image drape) and 3D vector (explode) functions.