Selecting features

Esri Redistricting allows you to select geography layers by attribute or by location for district assignment. This capability allows you to search for geographies that meet defined attributes, such as specific demographic variables, or that meet defined spatial criteria.

The steps below outline different ways to select features using the query layer and data layer. The query layer describes the geometry and attributes that will be used to filter against the data layer. The query layer can be any input layer for query, such as census geographies, external feature services, or other reference data. The data layer is a specific census hierarchy, such as County, Tract, VTD, Block Group, or Block.

Selecting features by attributes

One of the selection methods you can use to select features in a layer is to select features using an attribute query. This is performed using the Select Features by Attributes tool.

Select Features by Attributes allows you to provide an SQL query expression. This is used to select features that match the selection criteria. You may find this tool helpful in locating geographies for district assignments.

1. On the Create ribbon, change the Active District drop-down menu to the desired district.

   Because the Select Feature by Location tool allows you to assign selections to the active district, you need to ensure the Active District drop-down menu is set to the desired district.

2. On the Create ribbon, from the Selection Level drop-down menu, choose the desired hierarchy.

   The selection level is used as the data layer in the Select Features by Attributes tool.

   The data layer is dependent on the plan hierarchy, for example, County-VTD-Block or County-Tract-Block Group-Block.

3. On the Create ribbon, click Selection Menu.
4. Click Select by Attributes.
5. Create an SQL expression using one of the following methods:
   • Create a query using the expression building tools.
   • Type a query into the selection window.
   • Load a query saved to disk.

   Tip:

   Click Unique Values to see the values for the selected field when creating a query expression.

6. Choose how to apply the selection results:
   • One Stage automatically assigns the selection results to the active district.
   • Two Stage allows you to preview the selection results on the map before assigning to the active district.

   Caution:

   The assignment type will assign geographies or propose geographies to the active district, or both. Ensure you change the active district to the desired district before proceeding. The active district can be changed on the Create ribbon by selecting the district from the Active District drop-down menu.

7. Click Apply.

   The features are selected on the map. The assignments are determined by the assignment choice selected above.

   If you selected One Stage assignments, the selection results will automatically be assigned to the active district. For more information on One Stage assignments, see One Stage geography assignment.

   If you selected Two Stage assignments, the selection results are highlighted on the map. You can click the Proposed tab on the District Window to view all districts affected by the proposed assignment. For more information on Two Stage assignments, see Two Stage geography assignment.

Selecting features by location

The Select Features by Location tool works in conjunction with geography assignments, such as One Stage and Two Stage assignments. The Select Features by Location tool allows you to provide an SQL query expression that is used to select features that match the selection criteria.

For example, you may use the Select Features by Location tool to locate all districts where the Black voting age population (Black18) is greater than 25,000, or you can apply a spatial filter by locating all districts that match your criteria above and that intersect a defined geographic region. The Select Features by Location tool also allows you to filter the data layer by specific attributes.

The Select Features by Location tool is versatile and will allow you to select features using different filter methods. Once selected, you can assign features using the One Stage or Two Stage geography assignment methods.

Filter the query layer by attribute

The Filter the query layer by attribute option allows you to create an SQL query expression using attributes from the query layer.

1. On the Create ribbon, from the Active District drop-down menu, choose the desired district.

   Because the Select Feature by Location tool allows you to assign selections to the active district, you need to ensure the active district drop-down menu is set to the desired district.

2. Zoom to the desired data layer if you will be including a data layer attribute query (optional).

   The data layer is dependent on the plan hierarchy, for example, County-VTD-Block or County-Tract-Block Group-Block. The current display level determines the data layer used in the data layer attribute query.

3. On the Create ribbon, click Selection Menu.
4. Click Select by Location.
5. Choose a query layer from the drop-down menu.
6. Choose a spatial relation from the drop-down menu.
7. Check the Filter by Attribute option.

   The Filter the Query Layer by Attribute option expands to display a query builder.

8. Create an SQL expression using the query builder.

   To add a field to the expression, double-click the field. Click a field to enable the Get Sample Values button. Click the Get Sample Values button to view sample values for the selected field.

9. In the query layer frame, apply the Filter Spatially option in conjunction with your feature selection (optional). For more information on how to apply the spatial selection, see Filter the query layer spatially.

   The query layer can be any input layer for query, such as census geographies, external feature services, or other reference data.

10. In the data layer frame, apply the Filter the data layer by attribute option (optional). For more information on how to apply data layer attributes, see Filter the data layer by attribute.

    The data layer is a specific census hierarchy, such as County, Tract, VTD, Block Group, or Block.

11. Choose how to apply the selection results:
    • One Stage automatically assigns the selection results to the active district.
    • Two Stage allows you to preview the selection results on the map before assigning to the active district.

    Caution:

    The assignment type will assign geographies or propose geographies to the active district, or both. Ensure you change the active district to the desired district before proceeding. The active district can be changed on the Home ribbon by selecting the district from the Active District drop-down menu.

12. Click Apply.

    The features are selected on the map. The assignments are determined by the assignment choice selected above.

    If you selected One Stage assignments, the selection results will automatically be assigned to the active district. For more information on One Stage assignments, see One Stage geography assignment.

    If you selected Two Stage assignments, the selection results are highlighted on the map. You can click the Proposed tab on the District Window to view all districts affected by the proposed assignment. For more information on Two Stage assignments, see Two Stage geography assignment.

Filter the query layer spatially

The Filter the query layer spatially option allows you to draw a region spatially on the map to select features from the query layer.

1. On the Create ribbon, from the Active District drop-down menu, choose the desired district.

   Because the Select Feature by Location tool allows you to assign selections to the active district, you need to ensure the active district drop-down menu is set to the desired district.

2. If you include a data layer attribute query, zoom to the desired data layer (optional).

   The data layer is dependent on the plan hierarchy, for example, County-VTD-Block or County-Tract-Block Group-Block. The current display level determines the data layer used in the data layer attribute query.

3. On the Home ribbon, click Selection Menu.
4. Click Select by Location.
5. Choose a query layer from the drop-down menu.
6. Choose a spatial relation from the drop-down menu.
7. Check the Filter Spatially option.

   The Filter Spatially option expands to display selection tools.

8. Click to enable one of the selection tools.

Selection tools include the following:

• Draw a point allows you to select a geography by point selection.
• Draw a rectangle allows you to select geographies by rectangle selection.
• Draw a polygon allows you to select geographies by polygon selection.
• Draw a line allows you to select geographies using a line selection.
9. Define a geography selection on the map.

   The geography selection is displayed on the map. A Delete button appears on the Select Features by Location dialog box. This allows you to delete your geography selection to define a new spatial selection.

10. In the query layer frame, apply the Filter by Attribute option (optional). For more information on how to apply query layer attributes, see Filter the query layer by attribute.

    The query layer can be any input layer for query, such as census geographies, external feature services, or other reference data.

11. In the data layer frame, apply the Filter by Attribute option (optional). For more information on how to apply data layer attributes, see Filter the data layer by attribute.

    The data layer is a specific census hierarchy, such as County, Tract, VTD, Block Group, or Block.

12. Choose how to apply the selection results:
    • One Stage automatically assigns the selection results to the active district.
    • Two Stage allows you to preview the selection results on the map before assigning to the active district.

    Caution:

    The assignment type will assign geographies or propose geographies to the active district, or both. Ensure you change the active district to the desired district before proceeding. The active district can be changed on the Create ribbon by selecting the district from the Active District drop-down menu.

13. Click Apply.

    The features are selected on the map. The assignments are determined by the assignment choice selected above.

    If you selected One Stage assignments, the selection results will automatically be assigned to the active district. For more information on One Stage assignments, see One Stage geography assignment.

    If you selected Two Stage assignments, the selection results are highlighted on the map. You can click the Proposed tab on the District Window to view all districts affected by the proposed assignment. For more information on Two Stage assignments, see Two Stage geography assignment.

Filter the data layer by attribute

The Filter the data layer by attribute option allows you to filter your selection by attributes in the data layer.

1. On the Create ribbon, from the Active District drop-down menu, choose the desired district.

   Because the Select Feature by Location tool allows you to assign selections to the active district, you need to ensure the Active District drop-down menu is set to the desired district.

2. Zoom to the desired data layer.

   The data layer is dependent on the plan hierarchy, for example, County-VTD-Block or County-Tract-Block Group-Block. The current display level determines the data layer used in the data layer attribute query.

3. On the Home ribbon, click Selection Menu.
4. Click Select by Location.
5. Choose a query layer from the drop-down menu.
6. Choose a spatial relation from the drop-down menu.
7. Check the Filter the Data Layer by Attribute option.

   Caution:

   The data layer is automatically determined by the display level. Zoom in or zoom out from the map to change to the desired data layer. For example, you may need to zoom in if the desired data layer is Tract; you will need to zoom in on the map to display tracts.

   The Filter the Data Layer by Attribute option expands to display a query builder.

8. Create an SQL expression using the query builder.

   To add a field to the expression, double-click the field. Click a field to enable the Get Sample Values button. Click the Get Sample Values button to view sample values for the selected field.

9. In the query layer frame, apply the Filter by Attribute option (optional). For more information on how to apply query layer attributes, see Filter the query layer by attribute.

   The query layer can be any input layer for query, such as census geographies, external feature services, or other reference data.

10. In the query layer frame, apply the Filter Spatially option in conjunction with your feature selection (optional). For more information on how to apply the spatial selection, see Filter the query layer spatially.
11. Choose how to apply the selection results:
    • One Stage automatically assigns the selection results to the active district.
    • Two Stage allows you to preview the selection results on the map before assigning to the active district.

    Caution:

    The assignment type will assign geographies or propose geographies to the active district, or both. Ensure you change the active district to the desired district before proceeding. The active district can be changed on the Create ribbon by selecting the district from the Active District drop-down menu.

12. Click Apply.

    The features are selected on the map. The assignments are determined by the assignment choice selected above.

    If you selected One Stage assignments, the selection results will automatically be assigned to the active district. For more information on One Stage assignments, see One Stage geography assignment.

    If you selected Two Stage assignments, the selection results are highlighted on the map. You can click the Proposed tab on the District Window to view all districts affected by the proposed assignment. For more information on Two Stage assignments, see Two Stage geography assignment.

You can select geography layers by attribute or by location for assignment in the districting plan.