Thiessen Polygons: Point Entities

Aim:

To create a Thiessen Polygons for the given Map using the chosen Point attributes.

Procedure:

Concept:   Entities have area of Influence, which we can tag as “Service Areas” or “Sphere of Influence”. For Example, Post Offices that cater to particular zone, Places of religious worship that is accessible to the residents of a particular zone,…   Now, though these are completely two different entities, there could be instances where a particular feature types is repeated at a closer proximity within a zone.  Example, a section in the zone which has two temples. Now which temple would be more proximate to which part of the zonal section?  Another more obvious example will be habitats which have their own spatial areas of habitation, there is no physical or political boundary here, but just the sphere of influence, based on the distance between two or more entity features.  The non-uniform spread of features uses its own distance weighing attributes to compute Influential Zones of Polygons.

Step 1: Map Input

Identify the Point entities component for the location dataset. For this session, Post Offices and Temples (Hindu Place of Worship) were digitized from the given topographic map of Nellore & Cuddapah Districts.  The Point Entities were saved as “Civic Areas”.

Step 2: Map Processing

• ·         Digitize the Point Entities for Selected entities. Perform Attribute Editing. “Add Field” for “Name” and “Weights”.  Specify the Name (Temples or PO) in the Attribute Window.
• ·         Locate the “Create Thiessen Polygons” tool in Analysis -> Proximity, toolbox.
• ·         Define the Tool Input “Civic Areas” 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

Conclusion:

Thiessian Polygon maps for the chosen polygon  attributes are generated using ArcGis 10.1.