Spectrum - Query of a Query

This guide explains how to perform a "query of a query" in Spectrum Spatial. This method is useful when selecting property parcels within a specific zone, particularly when manual selection is impractical due to the complexity or size of the area.

Step 1: Initial Query on Planning Zones

The first step is to filter the planning zones to isolate the desired zoning type.

1. Open the Planning Zones layer.

   Perform a query within the visible map area:

   • Select the Custom Filter option.
   • Apply the condition: Zone = 'Low Density Residential'
2. Click "Create" to generate the query.
3. Turn off the Zone Layer and Prop Map to focus on the queried results.

At this stage, the results may contain unwanted areas (e.g., low-density residential zones outside the target region). To refine the selection, proceed with the polygon selection method.

Step 2: Refining the Selection Using Polygon Select

1. Click the three-dot menu on the query result and select Multi-Select.
2. Use the Polygon Selection tool to manually select the relevant features.
3. The selected features will appear in the left-hand panel.

Limitations of Spectrum Spatial Queries

• Spectrum does not allow direct passing of query results to another query.
• You must manually convert selected features into annotations to use them in the next query.

Step 3: Convert the Selection into Annotations

1. For each selected polygon, manually click "Add as Annotation" in the query results panel.
2. Once all features are added, turn off the previous query layer to keep only the annotations.
3. The annotations folder should now contain the selected features.

Step 4: Apply a Negative Buffer to the Annotations

Due to a slight misalignment between planning zones and cadastral boundaries, an unwanted selection of adjacent parcels may occur. To prevent this, apply a negative buffer to contract the polygons slightly.

1. Apply a negative buffer of -0.5 metres to each annotation.
2. This adjustment ensures that the selection does not include parcels extending beyond the intended zone boundary.
3. Verify the buffer effect by zooming in on a boundary to confirm that the annotations have shrunk away from the parcel lines.

Step 5: Query Property Parcels Using Annotations

Now that the annotations represent the refined zone selection, use them to query property parcels.

1. Click the three-dot menu on the Annotations folder.

   Select "Query in Selected".

   In the query settings:

   • Choose Prop Map as the target layer.
   • Add an optional filter (e.g., PID != 0 to exclude properties without an identifier).
2. Click "Create" to execute the query.

Step 6: Export the Results

• The query results now display property parcels within the selected zones.
• You can export the results as a CSV or process them further as needed.

Final Notes

• This method allows for the precise, automated selection of parcels within specific zones.
• If dealing with more than five polygons, the process can become cumbersome. In such cases, consider alternative workflows in MapInfo or consult a GIS expert for a more efficient approach.