The union operation combines and preserves all features and corresponding attributes from a set of input feature class layers.
How the Union Operation Works
Access the tool from eRAMS GIS Tool > Geoprocessing > Feature Class > Overlay > Union
- The operation creates polygons that are unique combinations of the features from input layers.
- Union requires that both feature layers to be polygon layers.
- The order of entries in the list of input feature layers does not affect the output layer spatial features or attributes.
- The extent of the output layer is the combined extent of the input layers.
- The number of features in the output layers varies with the number of unique incidences of features in the input layers.
- All attributes from input layers are included in the attribute table of the outputs layer.
- The feature IDs of input layers are included in the attribute table of the output layer.
- The attributes from input layers are represented as separate fields in the output layer attribute table, even when the field names are the same.
- The values of the attributes from input fields are obtained from the corresponding input layers and are left blank for output features that are not encompassed in the input layer.