The Georeference Tool lets users spatially position data that does not already have real-world coordinates assigned to it. It works by letting users place matching control points, one set on the source data and one set on a georeferenced destination, so SKAND can calculate the correct spatial transformation and apply it.
This is particularly useful for 2D floor plans, imported images, point clouds, or any layer that was processed without GPS or coordinate metadata.
Note: At least three (3) control point pairs are needed to apply a georeference transformation. More control points generally produce a more accurate result.
How It Works
Georeferencing works by establishing a spatial relationship between two datasets: the source (the data to be positioned) and the destination (a layer that already has known real-world coordinates, such as a point cloud or a base map).
For each control point pair, users identify the same physical location in both the source data and the destination. SKAND uses these matched pairs to compute a transformation, then repositions and rescales the source data so it aligns correctly in real-world space.
How to Use
Open the Georeference Tool
1. Open the project and go to the Layers tab in the left panel. This is the layer without valid coordinates assigned, referred to as the source layer.
2. Select Georeference from the Layering tab. The Georeference Tool panel will open.
Note: If the destination viewport appears empty, ensure at least one georeferenced layer (such as a point cloud or 3D model with a valid EPSG code) is already published in the project. If no other option is available, users can use the built-in 2D basemaps as a reference.
Add Control Points
Control points are pairs of locations users mark on both the source and the destination that correspond to the same physical spot. Adding accurate control point pairs is the most important step in the georeferencing process.
3. Add a Control Point on the Source
Click on a clearly identifiable location in the source layer, such as a corner of a room, a column, or any other recognizable feature. A red annotation will appear and will correspond to the source control point.
4. Add the Matching Control Point on the Destination
Navigate to the same physical location in the destination layer and click to place the matching point. The control point pair is now registered and will appear in the Control Points list in the panel.
Add More Control Points
5. Repeat the process to add additional control point pairs. A minimum of three pairs is required before the transformation can be applied.
Pro tip: For best results, spread control points across different areas of the data rather than clustering them in one region.
Use corners, intersections, or other sharp, well-defined features as control points. Avoid placing pins on curved or ambiguous surfaces where the exact center is hard to locate.
Edit or Remove a Control Point
6. To adjust or remove an existing control point pair, click on the pair in the Control Points list. A control point can be repositioned by dragging it in either viewport or the pair can be deleted entirely using the Remove button next to the entry. Destination control point coordinates can be edited as well.
Apply Georeferencing
7. Review the control point pairs in the list. Check that none of them show a high residual error value. A high residual for a specific pair may indicate that the control point placement was imprecise.
8. Once confirmed, click Done. SKAND will calculate the transformation and reposition the source layer in real-world coordinates. Once complete, the source layer will be visible in its correct real-world position in the 3D scene.
Note: To adjust the positioning afterward, users can reopen the Georeference Tool, modify the control points, and apply again or use the Transformation tools.
Best Practices
Dynamic Ortho Layer Elevation: When working with ortho layers, plane fighting may occur if the layer height is set too low. To avoid this, set the layer height to a minimum of 0.001 m.
Minimum control points – Three pairs are required for a valid transformation. More pairs improve accuracy and reduce error introduced by any single imprecise placement.
Spread control points – Place pairs at different corners or edges of the dataset. Control points that are too close together or all in one area will produce unreliable results for the rest of the data.
Check individual control point pair errors – The control point list shows a residual error value for each pair after the transformation is calculated. Pairs with noticeably higher residuals than the rest are candidates for adjustment or removal.
Destination layer quality – The accuracy of the georeferenced result depends on the accuracy of the destination layer itself. Using a high-quality, well-calibrated destination layer as the reference will produce better outcomes.
Supported source types – The Georeference Tool can be used on all layers and data types that lack coordinate metadata.