Creating Redistricting Plans

When iRedistrict for Site is launched, both the unit layer and the school layer are shown on the map. By default, equal population and compact shape is selected as the redistricting goals. # of District is set as the number of the sites, which cannot be changed.

When iRedistrict is launched, only the unit layer is shown on the map. In the example below, we use Utah block groups as the unit for redistricting. The Population attribute is used as the primary optimization factor. The map is visualized according to the population density. The visualization attribute can be changed at the bottom left corner of the map.

Set Redistricting Criteria

Criteria	Description	Assigning factors to Each Criteria
Population	The balance of the population across units	a. Select the attribute that is associated with the population data to be considered in the optimization b. Set the weight* c. Set the threshold**
Shape	The compactness of the shape of each unit	Set the weight*
Balance of multiple variables	The balance of each selected variable across units	a. Set the threshold** b. Select the attribute(s) that you would like to balance within the optimization c. Set the weight *
Similarity	The similarity of attribute values within target regions	Set the weight *
Distance***	Minimizes the total distance between each unit polygon and the site it is assigned to (weighted by the population of each polygon)	a. Set the weight* b. A point-to-point distance network is created by default. ZillionInfo can host a road network distance file if you are able to provide it.
Boundary	Preserve existing boundaries as much as possible	a. Set the weight* b. The boundary data must be pre-published.

The weight is the importance of a factor in comparison to the other factors enabled within the criteria. It should be a positive integer if the criterion is to be considered in the optimization algorithm. The weight can be set to zero if the factors, such as population, is not to be considered.

The threshold is the tolerance limit compared to target value of the population. For example, if the population threshold is 5% and the target value is 10,000, the population could range between 9,500 and 10,500 as a result.

The distance criterion is optimal for datasets with sites, and it is not applicable for datasets without sites.

Set Algorithm, Number of Districts, and Number of Plans

Algorithm: Pick the algorithm, for faster speed or better optimization results.

#Districts: Specify the number of districts you plan to generate. For iRedistrict for Site, this number equals to the number of site, which cannot be changed.

#Plans: Specify the number of plans to be created. # of Plans is set as 10 by default. It can be changed. We limit it to be no higher than 50 so that one user won't take the server resources for too long. For on-premise deployment, this number could be changed.

Click Run to Create Redistricting Plans

Click Run button to start creating redistricting plans.

On the right part of the screen, the "Request" tab shows how many plans are calculated. Click "Stop" to stop the calculation. However, it doesn't stop immediately. If the calculation is in the middle of one plan generation, it stops after this plan is created and wouldn't calculate the remaining plans.

After clicking the "Run" button, you can choose to wait in front of the screen or leave for the meeting and other works.

If you wait in front of the screen, once the calculation is finished, a dialogue is shown to ask you permission to display the results. Click "Yes" to load plans on the map.

If you close the browser session and leave to do other works, when you go back, launch this redistricting project, you see the calculation process in the "Request" tab. If the calculation is done, you see the green buttons that shows your previous calculation. Click the "Load" button to show plans created.

The image below shows the plans created.