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Identify Changes

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This documentation is primarily generated by AI and may contain inaccuracies or incomplete information. A thorough manual review is still pending. Please Report any errors, inconsistencies, or suggestions for improvement to ensure accuracy and reliability.

The "Identify Changes" algorithm is a tool designed for QGIS to detect and highlight differences between two vector layers: a Reference Layer and a New Modified Layer. This tool supports Point, Line, and Polygon geometries, and it outputs the differences in vertices and geometries as new layers. It is ideal for tasks such as validating changes in cadastral surveys or GIS projects.

Data Required​

ColumnExpecting Value (Description)Type
New Modified LayerThis is the updated shapefile containing the changes. Ensure this layer is free of topology errors for accurate results. Supported geometry types: Point, Line, or Polygon.Shapefile
Reference LayerThis is the original shapefile used for comparison. Supported geometry types: Point, Line, or Polygon.Shapefile
Changed VerticesThe output layer for modified vertices. Default: Temporary layer.Path
Changed FeaturesThe output layer for modified geometries. Default: Temporary layer.Path
Open output file after running algorithmOption to automatically open the output layer in QGIS Project after running the algorithm. Default: Yes.Boolean
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This Algorithm supports batch process

How to​

1. Run the algorithm​

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Ensure any pending edits are committed before running this tool. Layers must have the same CRS for accurate results.

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Ensure any pending edits are committed before running this tool. Layers must have the same CRS for accurate results.

  1. Open the "Identify Changes" under Bhukamatha tool in the QGIS processing toolbox.

  2. Select the required input layers.

  3. Specify output paths for Changed Vertices and Changed Result (or leave them as temporary layers).

  4. Click Run to start the algorithm.

2. View Results​

  • The results will be added to your QGIS project (Open output file after running algorithm is checked):
    • Changed Vertices will highlight all modified vertices.
    • Changed Features will show all modified geometries, with appropriate naming (e.g., Changed Points, Lines, or Polygons).

Expected Results​

  • A Changed Vertices layer showing all modified points across the two input layers.
  • A Changed Features layer showing altered geometries,Temporary outputs are dynamically named for convenience (e.g., Changed Points, Lines, or Polygons).

Error Messages​

  1. Reference Layer is Invalid

    • Ensure the selected Reference Layer is a valid vector layer.

  2. Changed Features is Invalid

    • Verify the New Modified Layer is correctly loaded and free of topology errors.

Limitations​

  • This tool may be computationally intensive for very large datasets.
  • Topology errors in the New Modified Layer can lead to inaccurate results.

Tips for Best Results​

  1. Check Topology

    • Validate and clean your shapefiles to ensure accuracy.
    • Use QGIS's built-in topology checker.

  2. Use Spatial Indexing

    • If working with large datasets, ensure spatial indexing is enabled for better performance.

  3. Save Outputs

    • While temporary layers are created by default, saving outputs ensures you retain results after QGIS is closed.