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📌Land Parcel Numbering Tool

Available from v3.0.0

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This tool provides comprehensive functionality for interactively numbering land parcels in QGIS. It combines manual control with powerful auto-numbering algorithms designed for different parcel layouts.

🌟 Key Features​

  • Advanced Auto-Numbering Dialog: Configure custom fields, start corners, custom start features, flow directions, sorting patterns, and algorithms.
  • Interactive Visual Preview: Visualize the proposed numbering path and sequence numbers on the map canvas before committing.
  • Intelligent Manual Numbering: Click-to-assign with automatic duplicate detection and smart sequence tracking.
  • Edit Mode Auto-Detection: Automatically handles layer locking/unlocking.
  • Data Integrity: Built-in safeguards against accidental data overwrites.
  • Visual Feedback: Color-coded symbology to instantly see status (Duplicates, Edited, Auto-numbered).

🛠️ The Toolbar Interface​

The toolbar is vertically split into Map Tools (Left) and Data Tools (Right).

Map Tools (Left Side)​

Use these for navigation and numbering operations.

  1. Zoom In / Out: Standard map navigation.
  2. Pan: Click and drag to move the map.
  3. Smart Select: Draw a rectangle to select a subset of parcels. Only selected parcels will be auto-numbered.
  4. Deselect: Clear the current selection.
  5. Auto Number Settings (Gear/Snake Icons): Opens the advanced Auto Number Settings dialog.
  6. Manual Numbering (Crosshair): Point-and-click numbering tool.

Data Tools (Right Side)​

Use these to manage the underlying database.

  1. Open Attribute Table: Opens the standard QGIS attribute table for the layer.
  2. Delete Label Field (Trash Icon): Opens a multi-select dialog to delete fields (e.g., to clear LP_NO and start fresh).

⚙️ Advanced Auto-Numbering Dialog Settings​

When you launch the Auto Number tool, a dialog with the following settings will appear:

  • Field Name: An editable combobox where you can select an existing attribute field (defaults to LP_NO) or type a new field name to create it.
  • Start Number: A numeric input indicating the starting sequence number. The tool automatically detects and defaults to last max value + 1 or 1 if empty.
  • Start Corner: Choose which quadrant of the target area to begin numbering from:
    • Top-Left (NW)
    • Top-Right (NE)
    • Bottom-Left (SW)
    • Bottom-Right (SE)
  • Manual Start (Selected Start): Click the "Select on Canvas..." button and click directly on a parcel in the QGIS canvas. The numbering sequence will begin exactly at this parcel, overriding the default mathematical corner.
  • Flow Direction:
    • Row-wise (Horizontal): Groups features into horizontal rows and numbers them along the X-axis.
    • Column-wise (Vertical): Groups features into vertical columns and numbers them along the Y-axis.
  • Pattern:
    • Serpentine (Snake): Reverses the sequence direction on every alternate row or column, creating a continuous winding flow.
    • Z-Pattern: Numbers each row/column in the same direction, resetting back to the start side for the next row/column.
  • Algorithm:
    • Smart (Adjacency): Guided by adjacency checks. It traverses greedily to adjacent features sharing a boundary, prioritizing local neighbors and larger shared boundaries. Ideal for irregular or curved parcel layouts.
    • Original (Strict Grid): Follows the coordinates and sorting pattern strictly. Recommended for clean grid/checkerboard layouts.

🧬 Spatial Sorting & Adjacency Logic​

To handle tilted grids and irregular parcels, the "Smart" auto-numbering algorithm runs the following steps under the hood:

  1. Dominant Angle Detection: Analyzes segment orientations to compute the dominant angle.
  2. Coordinate Rotation: Rotates the coordinates of the feature centroids by the dominant angle to align the grid axes.
  3. Row/Column Grouping: Groups centroids into rows or columns using a spatial tolerance (e.g., 0.75 * avg_height for rows) before sorting.
  4. Adjacency Guided Traversal: Traverses features starting from Rank 0, jumping to the neighbor with the largest shared boundary to keep numbering contiguous.

👁️ Visual Numbering Preview​

Before applying the numbering to your database:

  1. Click the "Preview" button in the dialog.
  2. A green dashed path line (QgsRubberBand) will appear on the canvas connecting the centroids of the parcels in the calculated sequence.
  3. Sequence numbers will be rendered on the map canvas as a temporary layer so you can inspect the flow.
  4. Change settings (e.g., swap start corner or pattern) and click "Preview" again to see the updated path instantly.
  5. Click "OK" to write the numbers to the attribute field and clear the preview, or click "Cancel" to discard.

📖 Step-by-Step Usage​

Auto-Numbering Workflow​

  1. Select (Optional): Use the Smart Select tool to highlight a block of parcels. If nothing is selected, the entire layer is processed.
  2. Open Settings: Click the Auto Number icon to open the settings dialog.
  3. Configure: Select the target field, start number, corner, flow direction, pattern, and algorithm.
  4. Preview: Click Preview to visually verify the path on your map canvas.
  5. Apply: Click OK to write the numbers.

Manual Numbering Workflow​

  1. Click the Manual Numbering (Crosshair) tool.
  2. Basic Assignment: Left-click on a parcel to assign the current sequence number.
  3. Advanced Swiping (Drag to Label):
    • Right Click + Drag: Draw a line across multiple parcels. Any parcel the line touches will be numbered in sequence instantly.
    • Ctrl + Left Click + Drag: Alternative way to draw a numbering line.
  4. Editing: Hold Alt + Click on a parcel to edit its existing number.
  5. Duplicates: If you assign a duplicate number, the tool will warn you and highlight duplicates in Red.

🎨 Symbology & Status Codes​

The tool automatically applies a rule-based style to help you visualize progress.

ColorStatusMeaning
Green 🟢UniqueValid, unique number.
Red 🔴DuplicateThis number exists on multiple parcels.
Yellow 🟡EditedManually changed by user (tracked for quality control).
Blue 🔵ClearedWas a duplicate, but you fixed/cleared it.
Gray ⚪NullUnnumbered parcel.

Note: The tool tracks these states in a hidden STATUS field (auto, manual_edit, duplicate, etc.) for your reference.

⚡ Power User Tips​

  • Clean Slate: To completely restart, use the Delete Label Field (Trash Can) to delete the LP_NO field.
  • Keyboard Shortcuts:
    • Ctrl + Z: Undo the last manual action.
    • Ctrl + Y: Redo.
    • Alt + Click: Edit a specific label.
  • Performance: For layers with 10,000+ parcels, Select a smaller area before auto-numbering. Processing the entire layer at once may take a few seconds.

❓ Troubleshooting​

"Layer is not in edit mode"

  • The tool now handles this! Just click "Yes" when prompted to start editing.

"My numbers are jumping across the street!"

  • Try the Smart (Adjacency) algorithm. It is better at detecting "local neighbors" than the strict grid algorithm. Also verify that you have chosen the correct flow direction (Row-wise vs Column-wise) matching the road layout.

"I can't see the labels!"

  • Click the Refresh button in QGIS or toggle visibility. Ensure the specified field exists (use the Attribute Table button to check).