Overlay Analysis: Symmetrical Difference

Aim:

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

Procedure:

Concept:  Symmetrical Difference is the opposite of Intersect. All the non-common feature areas of two of more selected layers will be generated into a new output.

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 “Symmetrical Difference” tool in Analysis -> Overlay, toolbox.
• ·         Define the Tool Input “Forest” and SD layers feature 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:

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