Overlay Analysis: Identity Map

Aim:

To create perform overlay analysis of two (digitized) Feature datasets, using  identity method.

Procedure:

Concept:   Identity tool performs a kind of overlay analysis, where features in the new dataset or Target layer will wholly be retained, while selected features from the other layer (Old layer, usually), which overlap the new or target layer, will be retained.

Step 1: Map Input

Identify the two layers that can be digitized from your toposheet or base map. For this session, Forest Area and Waterbodies (Perennial) were digitized from the given topographic map of Nellore & Cuddapah Districts.  The Polygon Entities were saved into respective shapefiles in target ArcCatalog Folders.  

Step 2: Map Processing

• ·         Digitize the Polygon features for Selected entities. Perform Attribute Editing. “Add Field” for “Name” and “Area”.  Specify the Names and calculate geometry to calculate shape area.  (note to calculate geometry, the features need to be on Projected coordinate system).
• ·         Locate the “Identity” tool in Analysis -> Overlay, toolbox.
• ·         Define the Tool Input “Forest” and identity layer as “waterbodies” and specify the target output folder.
• ·         Click “Ok” to generate the map output

Step 3: Map Display

Create Custom Map Layout with the necessary map elements and Export map to Jpeg format. It’s best to display map outputs in three data frames, one for the Overlay Output ad two for displaying the input feature classes.  One may also choose to Add Attribute table to layout, an option available within the Table options.

Conclusion:

Identity map for the chosen polygon attributes layers are generated using ArcGis 10.1.