Union in ArcGis

In ArcGIS, the "Union" tool is a geoprocessing operation that combines the geometry and attributes of two or more feature layers to create a new layer. This operation creates an output layer that includes all the features from the input layers and attributes from each input layer. The "Union" tool is part of the broader suite of spatial analysis tools provided by ArcGIS.

Here's how the "Union" tool typically works:

Input Layers: You provide two or more input feature layers that you want to perform the union operation on.

Output Layer: The tool creates a new feature layer that contains the combined geometry and attributes from all the input layers. The output layer will include all the features from the input layers and will retain the attributes of each input feature.

Geometry Overlaps: The "Union" operation identifies the areas where the geometries of the input features overlap or intersect. It creates new polygons for these overlapping areas in the output layer.

Attribute Combination: For attributes, the "Union" tool combines the attribute information from each input layer. If there are overlapping features, the attributes from the overlapping areas are combined in the output attributes. This can be helpful for analyzing overlapping or intersecting geographic features and their associated attributes.

The "Union" tool is often used for various spatial analysis tasks, including:

Identifying areas of overlap or intersection between different layers.
Combining attributes from multiple layers to create a comprehensive dataset.
Creating new polygons representing the overlapping areas of input polygons.
Analyzing and visualizing patterns where features from different layers coincide.
It's important to note that the "Union" operation can potentially result in an output layer with a larger number of features than the sum of features in the input layers, especially in areas of overlap. The tool can be found within the ArcToolbox in ArcGIS, and the specific options and behavior might vary slightly depending on the version of ArcGIS you are using.