Refine Operations (Pro Feature)

Refine operations apply precise geometric transformations to your 3D model using real-world reference data. Unlike manual adjustments, Refine operations leverage actual measurements—such as GPS coordinates—to automatically align, rotate, and scale your model to match real-world geometry.

Note: Refine operations are available exclusively for Pro users.

What Are Refine Operations?

When photogrammetry reconstructs a 3D model, the result is geometrically accurate in shape but may not be correctly oriented, scaled, or positioned in real-world space. Refine operations solve this by anchoring your model to real-world data, producing a georeferenced and properly scaled result automatically.

Refine operations are ideal for:

• Drone surveys that require georeferenced output
• Architectural documentation tied to geographic coordinates
• Models that need to be accurately placed in real-world maps or GIS systems
• Any workflow where real-world scale and position matter

Accessing the Refine Tab

Navigate to the Refine tab in the Replica interface to access refine operations.

Available Operations

1. Drone Coordinates (Beta)

Automatically align, rotate, and scale your 3D model using GPS metadata embedded in your dataset images. This operation reads the geographic coordinates recorded by the drone at the time of each shot and uses them as reference to correctly transform the model in real-world space.

Beta Notice: Drone Coordinates is currently in beta. Results may vary depending on GPS accuracy and image dataset quality. We recommend verifying the output before using it in critical workflows.

Requirements:

• Images in the dataset must contain GPS metadata (EXIF geolocation data)
• GPS data is typically embedded automatically by drones and GPS-enabled cameras

How it works:

Step 1 — Extract GPS Data

Click the Extract from Project Images button.

Replica scans all images in your project, extracts the embedded GPS coordinates, and displays them in a table. Each row in the table corresponds to one image with its latitude, longitude, and altitude values.

Tip: Review the table to verify that GPS data was correctly read. If the table is empty or shows unexpected values.

Step 2 — Compute Transformation

Once you have reviewed the GPS data, click the Compute button.

Replica calculates the transformation needed to align the model with the GPS reference frame and applies:

• Translation — moves the model to the correct geographic position
• Rotation — orients the model to match the real-world heading
• Scale — adjusts the model size to match real-world distances derived from GPS positions

Step 3 — Review the Result

After the computation completes, a panel displays the geographic center of the model (latitude, longitude, and altitude). This confirms that the model has been successfully georeferenced.

Configuration options:

• None — the operation works automatically based on the GPS data extracted from images

Use cases:

• Drone surveys of terrain, buildings, or infrastructure
• Creating georeferenced models for GIS integration
• Architectural documentation with real-world positioning
• Volume calculations and measurements on correctly scaled models

Tip: For best results, capture images with a drone or camera that records accurate GPS coordinates. RTK (Real-Time Kinematic) drones provide centimeter-level accuracy, which yields the most precise transformations.

Best Practices

Ensuring Good GPS Data Quality

Use a GPS-enabled drone or camera:

• Consumer drones (DJI, Autel) automatically embed GPS in image EXIF data
• RTK drones provide higher accuracy for professional workflows
• Verify GPS logging is enabled before your flight

Plan your flight for good GPS coverage:

• Fly in open areas with clear sky visibility for better GPS signal
• Avoid flying near tall buildings or under canopies that block GPS signals
• Overlap your flight path sufficiently for good image coverage

Check your images before processing:

• Use a tool like ExifTool or a photo viewer to verify GPS metadata is present
• Ensure coordinates look plausible for your capture location
• Remove images with missing or clearly incorrect GPS data

Combining Refine with Workflows

You can use Drone Coordinates in combination with Workflows for a complete automated pipeline:

Example — Drone Survey Pipeline:

1. Run photogrammetry session
2. Apply Drone Coordinates (Refine tab) → georeferenced model
3. Apply Export Model (Workflow tab) → export as OBJ or GLB

Order matters: Apply Drone Coordinates before exporting so that the exported file includes the correct georeferencing transformations.

Troubleshooting

No GPS data found (empty table):

• Verify that your images contain GPS metadata using an EXIF viewer
• Check that GPS was enabled on your drone or camera during the flight
• Some image editing or conversion tools strip EXIF metadata — use original files

GPS data looks incorrect:

• Ensure the images are from the correct flight session
• Check for time zone or coordinate system inconsistencies
• Try removing outlier images with clearly wrong coordinates

Computation result seems inaccurate:

• The accuracy depends on the quality of the embedded GPS data
• Consumer drone GPS accuracy is typically 1–5 meters; RTK provides centimeter accuracy
• Verify the geographic center shown in the result panel matches the expected location
• Remember this is a beta feature — results may not be perfect in all scenarios

Scale seems off after computation:

• Ensure images were captured at consistent altitudes
• GPS-based scale estimation works best when images cover a large enough area
• For high-accuracy scale requirements, consider using Scale by Camera Distance from the Workflows tab as an alternative or complement

2. Measure & Scale

Manually scale your 3D model using real-world distance measurements, and optionally level it on the horizontal plane. This operation is ideal when GPS data is not available — for example, indoor captures, small object photogrammetry, or any dataset where you can physically measure known distances on the subject.

How it works:

You place pairs of points directly on the 3D model in the viewer and tell Replica how far apart they really are. With a single pair, Replica computes a uniform scale factor. With multiple pairs, it computes a best-fit scale via least squares, which significantly reduces error caused by imprecise clicks. Optionally, you can add a vertical reference pair that defines which direction should point straight up, and Replica will rotate the model to align that direction with the Y axis and translate it so the ground point sits at Y = 0.

Requirements:

• A completed photogrammetry session
• At least one real-world distance you can measure on the subject (e.g., the length of an A4 sheet, a book spine, a printed marker)

Tip: prepare your reference distances before capturing photos. Place a measured object (an A4 sheet, a ruler, a book) inside the scene so that it appears in your dataset images — you will use it later as the measurement reference.

Step 1 — Add a measurement pair

Click the Add measurement button to create a new measurement pair. Each pair consists of:

• Point A — first point on the model
• Point B — second point on the model
• Real (m) — the real-world distance between A and B, in meters

Click Point A to enter placement mode, then click on the 3D model where the first reference point is located. Repeat with Point B. Yellow markers appear on the model at the points you placed.

Once both points are placed, Replica shows the measured (model-space) distance next to the pair. Type the real distance in meters into the Real (m) field (decimals separated by a dot or comma both work).

Tip — use multiple pairs for better accuracy: add 2–3 measurement pairs covering different parts of the model. The least-squares solver will use all of them simultaneously, producing a more robust scale estimate than a single measurement.

If you misplace a point, click the small x next to the A ✓ or B ✓ button to clear just that point and place it again. To remove an entire measurement pair, click the red trash icon next to the pair name.

Step 2 — (Optional) Add a vertical reference

If your subject has a clear vertical edge (a wall corner, a pole, the spine of a book standing upright), use it as a vertical reference to automatically level the model.

Click Ground point and click on the floor or base of the subject. Click Top point and click on a point that is directly above the ground point — they should both lie along a real-world vertical line. Cyan markers appear at these positions, and a small fixed orange arrow at the origin indicates the world-up direction so you can see what Replica is targeting.

Step 3 — Apply

Click APPLY (scale + level). Replica:

• Computes the best-fit scale from all valid measurement pairs
• (If vertical reference is set) computes the rotation that aligns ground→top with world Y
• (If vertical reference is set) translates the model so the ground point sits at Y = 0
• Applies all three transformations in a single rigid transform

The model in the viewer updates immediately. The markers follow the transformed model, so you can verify visually that the measurements still make sense.

Configuration options:

• Number of measurement pairs — free, more pairs = more robust scale
• Vertical reference — optional, enables levelling and grounding

Use cases:

• Indoor photogrammetry where GPS is unavailable
• Small object capture (statues, products, archaeological finds)
• Architectural details where a printed reference of known size is included in the scene
• Any dataset where you want metric accuracy without relying on GPS

Tip: for the cleanest results, choose reference distances that are as long as possible and well-spread across the model. A single 30 cm measurement on one corner of a 2 m model is less accurate than two 1 m measurements spanning the whole scene.

Removing a Refine operation

When you click the Delete button on a Refine operation, Replica:

• Removes the operation from the list
• Resets the 3D viewer to the original, pre-refine model
• Cancels the applied state of all other Refine operations (you will need to re-compute them if you want their effect back)

This ensures the viewer and any subsequent export reflect the same state. If you want to keep multiple Refine operations active, simply leave them in the list — Delete is for fully starting over.

Next Steps

Now that you understand Refine operations:

• Getting Started - Learn the basics of creating photogrammetry projects
• Session Configuration - Master configuration options for optimal reconstruction
• Workflows (Pro) - Automate post-processing with scale, alignment, and export operations

Need Help?

Visit the Replica community forums for support and tips from other Pro users.

Happy georeferencing!