6.5.3. Union

The Union (Analysis) tool is used to create a geometric connection between polygon layers where all features and geometries will be added to the resulting layer. The union function is useful when the geometries and attributes of different layers should be merged. In ArcGIS, all input polygons will be transferred to the output layer, regardless as to whether they spatially overlap or not, leaving the resulting dataset with three feature types: those found only in the first input layer, those found only in the second input layer, and those found in both the first and second input layers (Ormsby et al., 2010).