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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​

  • Dual Auto-Numbering: Two distinct algorithms ("Smart" and "Original") to handle both organic and grid-like parcel layouts.
  • 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 (Smart serpentine - Green Snake): The default recommendation. Prioritizes local connections for a smooth flow.
  6. Auto Number (Original - Red Snake): A stricter algorithm. Prioritizes grid connectivity.
  7. 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).

🧬 Algorithm Deep Dive​

Understanding which algorithm to use can save you time.

1. Smart Serpentine (Green Snake) 🟢​

Logic: Rank-Anchored Local Search

  • How it works: It establishes a general "Rank" (Top-Left to Bottom-Right) but is allowed to "search locally" for the best neighbor.
  • Best For: Organic / Irregular Layouts. If your parcels have curvy roads or slightly offset grids, this algorithm flows naturally like a snake, minimizing long jumps.

2. Original (Red Snake) 🔴​

Logic: Connectivity-Constrained Strict Sort

  • How it works: It creates a "Virtual Grid" and moves strictly from one cell to the next. It prioritizes direct physical connectivity above all else.
  • Best For: Strict Grids. Use this when you have perfect checkerboard layouts and want to ensure the numbering never "jumps" across a street or gap unless necessary.

📖 Step-by-Step Usage​

Auto-Numbering Workflow​

  1. Select (Optional): Use the Smart Select tool to highlight a block of parcels.
    • Tip: Auto-numbering small blocks at a time allows for finer control over the sequence.
  2. Run Tool: Click either Green Snake (Smart) or Red Snake (Original).
  3. Configure:
    • Start Number: Enter the starting value (e.g., 101).
    • Overwrite: Check this if you want to replace existing numbers. If unchecked, it will skip already labeled parcels.
  4. Confirm: The tool will process the parcels and apply labels.

Manual Numbering Workflow​

  1. Click the Manual Numbering (Crosshair) tool.
  2. Basic Assignment: Left-click on a parcel to assign the current 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. This is extremely useful for quickly labeling rows of parcels like "swiping" a credit card.
  4. Editing: Hold Alt + Click on a parcel to edit its existing number.
  5. Duplicates: If you type a number that already exists, the tool will warn you and highlight the 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. Fix immediately!
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. This is cleaner than overwriting.
  • Keyboard Shortcuts:
    • Ctrl + Z: Undo the last 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 Green Snake (Smart) algorithm. It is better at detecting "local neighbors" than the strict grid algorithm.

"I can't see the labels!"

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