Geometry Repair Toolkit

The Geometry Repair Toolkit is a standalone dialog-based tool for validating, inspecting, and repairing polygon geometries. It provides a comprehensive interface for detecting and fixing common topology and geometry issues across your polygon layers into safe, temporary memory output layers.

Access

• Menu: Gemma → Others → Geometry Repair Toolkit
• Component Algorithm IDs: gmd_pipeline:scangeometryerrors, gmd_pipeline:repairpolygongeometries
• This tool opens as a separate dialog window (not through the Processing Toolbox).

When to Use

Use this tool when:

• You suspect polygon layers contain invalid, self-intersecting, or corrupted geometries.
• QGIS reports geometry errors during processing or spatial operations.
• You need to clean up and validate polygon layers before running other GMD tools (such as MBI Checker or Fill Polygon Gaps).
• You want to identify and fix null geometries, empty shapes, wrong geometry types, or duplicate features.

Features & Tab Structure

The toolkit features a tabbed interface:

1. Geometry Fixer (Tab 1) — Scan layers, inspect detected issues in an interactive table, highlight error geometries on the map canvas, and run automated repairs.
2. Help and Information (Tab 2) — View reference tables for error types, repair mechanisms, output layer behavior, and limitations.

Error Types Reference

The toolkit scans polygon layers for the following topology and geometry issues:

Error Type	Description	Repair Mechanism
Null Geometry	The feature record exists, but there is no geometry object.	Auto-fixable (Recovery from surrounding polygons)
Empty/Missing Geometry	The feature exists, but its geometry has no usable shape or coordinates.	Auto-fixable (Recovery from surrounding polygons)
Invalid Geometry	The polygon has geometry errors such as self-intersection, ring error, spike, or folded edge.	Auto-fixable (Polygon reconstruction)
Self Intersection	The polygon crosses itself.	Auto-fixable (Polygon reconstruction)
Wrong-type Geometry	The feature's geometry type does not match the layer's declared geometry type (e.g. a line or GeometryCollection stored in a polygon layer).	Auto-fixable (Polygon reconstruction)
Duplicate Geometry	Two or more features share the exact same geometry.	Requires manual review / deduplication
Dangle (Loose End)	A line endpoint doesn't connect to any other line.	Requires manual review

How to Use

1. Open the tool from Gemma → Others → Geometry Repair Toolkit.
2. Under Input Layers, select one or more polygon layers to check.
3. Click Scan Layers to initiate the background geometry scan.
4. Review the detected errors in the results table:
   • White rows: Auto-fixable issues.
   • Grey rows: Issues requiring manual review.
5. Double-click any row to zoom to the affected feature on the map. The toolkit places rubber-band outlines and vertex markers over problematic geometry locations.
6. Check the rows to repair (or click the checkbox in the first column header to select/clear all auto-fixable rows).
7. Click Repair Selected Features. The toolkit routes each checked row to its specific repair mechanism and creates a new temporary repaired memory output layer.
8. Re-run Scan Layers on the temporary output layer to verify all errors are resolved.

Repair Mechanisms & Output Layers

Repair Selected Features

When you click Repair Selected Features, the tool inspects each checked error row and automatically applies the appropriate repair mechanism:

• Invalid / Wrong-type / Self Intersection: Reconstructs the polygon shape and writes the result to a new temporary output layer.
• Null / Empty / Missing Geometry: Recovers missing shapes using spatial boundary context from surrounding polygons.

Multipart Resolution & Artifact Cleanup

Polygon reconstruction can occasionally leave a feature as a multipart polygon even if it started as a single part. When this occurs:

• The toolkit runs Multipart to Singleparts on only the touched features.
• Negligible fragment slivers resulting from reconstruction artifacts are automatically dropped.
• Genuine multi-part survivors sharing original feature attributes are re-merged back into a single multipart feature (preventing attribute row duplication).
• Pre-existing legitimate multipart features (such as a barangay with offshore islands) that were not repaired remain completely untouched.

Non-Destructive Memory Layers

• Original Source Data Protection: Source layers are never modified. All fixes create temporary memory layers.
• Attribute Field Preservation: Temporary output layers retain all original attribute fields for seamless export.
• Logging: The log panel records layer names, processed feature IDs, repair methods, recovery status, and notes.

Limitations & Review Best Practices

Recommended Workflow

Run the Geometry Repair Toolkit on your layers before using other processing tools like the MBI Checker or Fill Polygon Gaps. Invalid geometries can cause unexpected results in topological analysis.

Non-Destructive Operations

The toolkit always writes repaired features to new temporary memory layers. Your original input files/layers are never overwritten.

Limitations & Manual Review

• Visual Inspection: Always visually inspect the resulting temporary output layer before exporting or replacing source data.
• Re-Scan Verification: Run Check Validity or re-scan the output layer with Scan Layers to confirm no secondary errors remain.
• Deleted Feature Records: Completely deleted attribute records cannot be recovered by this tool.
• Edge Polygons: Edge polygons cannot be safely reconstructed when their outer boundary is unknown. If an edge polygon is missing, return it to the LGU for corrected boundary geometry.
• Manual Review: Complex topology issues such as Duplicate Geometry and Dangles require manual review and editing.