Scale settings
Set the real-world scale per set so distances and areas are measured correctly
What is scale?
The 3D geometry reconstructed by image linking (SfM) has no real-world size on its own. The shape is correct, but whether "1" means a metre or a centimetre is undefined.
Scale is the factor that converts that reconstructed coordinate system into real-world units (metres). Scale is a per-set setting, and it applies to every product generated from that set:
- Measurements on the orthomosaic
- Measurements on the 3D mesh
- Measurements on the cylindrical unwrap orthomosaic
- Measurements on the original (single) images
In other words, while scale is unset, distances and areas are not real-world values on any screen.
Launching
Open it from Process ▾ → Scale Settings on the toolbar. It applies to the currently selected set.
Scale cannot be computed for a set that has not been through image linking (SfM). Run Process ▾ → Image Linking / Orthomosaic Generation first.
This screen edits the same setting as Step 4 of the orthomosaic wizard.
Even if you never generate an orthomosaic (3D mesh only, or cylindrical unwrap only), you can set the real-world scale here at any time.
Screen layout
| Area | Contents |
|---|---|
| Image Selection | Visible-image thumbnails for the set. Images excluded from the project are not listed |
| View | The image you place two points on. Scroll to zoom, drag to pan |
| Current Scale | The factor in use and its source |
| Add Measurement | Known distance and unit input |
| Measurement List | List of registered measurements |
Adding a measurement
- Enter the known distance and choose the unit (m / cm / mm)
- Click two points on the image (right-click to cancel the selection)
- Click Add Measurement
Accuracy improves when you pick something whose dimension is certain and whose ends are clearly visible in the image — a door height, a window width, a known span.
Registering 2–4 measurements is recommended. With several measurements the median is adopted, so a single outlier will not badly skew the result. Measurements can be spread across different images.
Each row in the measurement list shows the difference between the factor derived from that measurement alone and the adopted value (the median). A row with a large difference usually means the clicked points are off, or the known distance was entered incorrectly.
Unchecking a row excludes that measurement from the scale calculation without deleting it.
Current scale (source)
| Display | Meaning |
|---|---|
| Not set (raw SfM scale) | No factor resolved. Displayed distances and areas are not real-world values |
| Source: N known-distance measurement(s) | Resolved from the measurements registered on this screen |
| Source: GPS (estimated from capture positions) | Estimated automatically from the capture positions |
When your images carry GPS, scale is estimated automatically from the capture positions. If you register known-distance measurements for the same image linking, those take priority, because a manual measurement is more reliable.
Clear Scale resets the factor to unset. The registered measurements remain, so you can re-enable them later.
What changes when you save
Save stores the resolved factor on the set and applies it to existing products.
| Applied to | Details |
|---|---|
| Orthomosaic | The real-world (metre) figures are updated. The orthomosaic image itself is not regenerated — pixel density does not depend on scale |
| Saved measurements | Distances and areas of measurements created under the same image linking (SfM reconstruction) are updated to the new scale. Measurement positions do not move |
| 3D view | Applied to the 3D mesh currently displayed |
If the factor cannot be resolved — for example when every measurement is rejected — nothing is applied to the products and you are told so. Your measurements are still saved, so add or correct them and save again.
After re-running image linking
A scale factor is stored together with the image linking (SfM reconstruction) it was derived from. Re-running image linking changes the scale of the reconstructed coordinate system itself, so the previous factor is no longer valid as-is.
However, the registered measurements (two points plus a known distance) remain. Reopening Scale Settings recalculates them against the current reconstruction, so you only need to press Save to apply the new factor — there is no need to place the points again.