Cylindrical unwrap
Unwrap tanks, silos, chimneys and other cylindrical structures into a single full-circumference image
What is cylindrical unwrap?
Structures with curved walls — tanks, silos, chimneys, round buildings — cannot be unwrapped correctly by the usual orthomosaic generation, which assumes flat planes. Generating one orthomosaic per face leaves the curved parts stretched or broken up.
Cylindrical unwrap fits a cylinder to the SfM point cloud and projects the images onto that cylindrical surface, unwrapping the full circumference into a single image. In the output, the horizontal axis is arc length around the circumference and the vertical axis is height.
Launching
Launch it from Process ▾ → Special orthomosaic → Cylindrical unwrap on the toolbar.
Cylindrical unwrap is a PRO plan feature. See Plans and features for details.
Prerequisites
Cylindrical unwrap has more prerequisites than ordinary orthomosaic generation.
| Requirement | Details |
|---|---|
| Image linking (SfM) is complete | Run Process ▾ → Image Linking / Orthomosaic Generation first |
| A 3D mesh has been generated | Required, because the mesh is used for occlusion testing. See 3D models |
| The 3D mesh matches the current SfM result | After re-running image linking, regenerate the 3D mesh as well |
| The full circumference has been captured | Cylinder fitting fails if only part of the structure was photographed |
If a requirement is not met, the cylinder check screen tells you why. When no 3D mesh exists, you can go straight to it with the Open 3D Mesh Generation Wizard button on that screen.
Wizard steps
Step 1: Set selection
Choose the target set. This step is skipped when the project has only one set.
Step 2: Cylinder check
A cylinder is fitted to the SfM point cloud to determine whether cylindrical unwrap is applicable. In the top view, confirm that the fitted circle (red) sits on the building ring (light blue).
The following information is shown as the result.
| Item | Description |
|---|---|
| Estimated radius | Radius of the fitted cylinder |
| Height range | Height range to be unwrapped |
| Unwrap width (full circumference) | Arc length of the full circumference |
| Circumference coverage | Proportion of the circumference actually captured |
| Circle fit inlier ratio | How well the cylinder fit matches |
| Images used | Number of images used for the unwrap |
| Scale | Where the real-world scale comes from (see below) |
Scale can be shown in three ways.
| Display | Meaning |
|---|---|
| Inherited from existing orthomosaic | Uses the scale of an already generated orthomosaic |
| Estimated from GPS (Helmert) | Estimated from the capture positions |
| Unresolved (still in scene units) | Real-world size is undetermined; the output mm/pixel is not guaranteed as a real-world figure |
If the scale is unresolved, register a known distance in Scale settings so the unwrapped image is based on real-world dimensions.
Step 3: Output settings
Choose the output resolution from 5 / 10 / 20 mm per pixel (default: 10 mm/pixel). The estimated output size is shown as you change it.
Output width is capped at 16,000 px; beyond that, the resolution is adjusted automatically.
Starting generation
Click Start Generation to begin. After the visible-image unwrap finishes, the infrared cylindrical unwrap is generated automatically as well (if there are no thermal pairs, generation completes with the visible image only).
About the output
- The output is a single image with the full circumference unwrapped (horizontal = arc length, vertical = height)
- Once generated, you can view and measure it in the orthomosaic viewer
- GeoTIFF is not exported — a cylindrical surface has no geographic coordinate system
- For sets whose scale is unresolved, the real-world mm/pixel figure is not guaranteed