Capture a LiDAR point cloud
Sweep a trench, structure or surface with the Points mode, read the live warnings, review coverage, and export a georeferenced LAS.
On this page
Points mode uses the LiDAR sensor to build a coloured point cloud of whatever you sweep across: an open trench, a kerb line, a wall, a stockpile. The cloud is saved with its georeference, a record of how the session went, and optionally the raw keyframes. You can export it as a LAS file in your project's coordinate system.
Before you start
- You need a LiDAR device: an iPhone Pro or iPad Pro. On other devices, the Points tile is greyed out.
- The project needs at least one asset, or you can lock a new point at the start.
- Allow camera access. If it's off, the capture screen says "Camera access is off for OpenSurvey3D. Turn it on in Settings › Privacy › Camera to capture." and Start capture stays disabled.
Capture a point cloud
- Go to Capture → New capture and tap Points.
- Check the preflight banner, then lock the start position. See Lock the scan position.
- The camera opens. Tracking starts straight away, but nothing is captured yet. Frame the area and wait for Tracking ready — frame the area, then start.
- Tap Start capture.
- Sweep slowly across the surfaces you want. Dots appear where the depth reading is confident.
- Walk a few metres during the capture if you can. The chip reads Walk 3 m more for a GNSS heading until you've walked far enough, then Heading from GNSS track.
- Tap Stop capture.
- Review the result, then tap Keep to save it or Retake to throw it away and go again.
When you tap Keep, the cloud is filed against the asset you anchored to. If you skipped the lock, the app asks which asset it belongs to.
The capture screen
| Element | What it shows |
|---|---|
| Cancel (top left) | Leaves without saving anything |
| Mesh | Draws Apple's live surface wireframe over the camera view, so you can see what the sensor has covered. On by default where the device supports it. The wireframe is only a guide and is never saved. |
| Highlight | Dims the camera view and colours points by depth confidence, which is useful for checking coverage |
| Timer chip | Elapsed time and point count, for example 1:24 · 312k points. With frame recording on, it adds frames and megabytes. |
| Position line | Your position source and fix type |
| Heading chip | Whether the scan's heading will come from your GNSS track yet |
Live warnings
While you capture, one line at the bottom tells you what's wrong right now and what to do. If nothing is wrong, it shows the coaching line "Sweep across surfaces — dots land where depth is confident". Warnings appear in this order of importance:
| Warning | What to do |
|---|---|
| Point store full — stop to save this sweep | The cloud holds up to 500,000 points. Stop, keep this one and start another. |
| Starting up — move the device slowly until tracking settles. | Wait a moment |
| Tracking was interrupted. Point at something you already scanned and hold still until it recovers. | This happens after a phone call or a pause, for example. No points are added until tracking recovers. |
| Moving too fast to track. Slow down — geometry captured now lands in the wrong place. | Slow down |
| Not enough visual detail to track. Point at textured surfaces, or add light. | Plain walls, water and darkness cause this |
| Slow down — depth smears at this speed | You're moving faster than 0.8 m/s |
| Device is hot; capture is throttling | Let the device cool for a full-length session |
The screen stays awake during a capture, so it won't lock mid-sweep.
Review before you leave
After Stop capture, the review screen shows the cloud in 3D, with the point count as its title. If the app found problems, a panel lists them under Worth another pass before you leave or Notes on this capture. The findings can include:
- Tracking was degraded for more than 20% of the session.
- Tracking dropped and recovered one or more times.
- You moved faster than 0.8 m/s for more than 3 seconds.
- More than 35% of the captured surface has fewer than 3 points per 10 cm cell, too sparse to measure from.
- The subject was seen from fewer than 4 directions, so anything facing away is missing.
- The device got hot enough to throttle.
When the panel says another pass is worthwhile, Retake is emphasised. It's still your call: the app can't know what you meant to capture, only how well the captured parts were covered.
If a sweep is too thin to use, with fewer than 500 usable points, the app doesn't save it. It says "Only … usable points — nothing to save. Sweep the surface slowly from closer in, and stop after a longer pass." and returns you to the ready screen at the same spot.
What's saved
Each point cloud is a folder attached to the asset:
| File | Contents |
|---|---|
points.ply |
Binary PLY: x, y, z in metres, RGB colour, and ARKit's confidence (0–2) per point, in the local gravity-aligned frame |
georef.json |
Where the local frame sits on the earth: origin, heading and its source, camera offset, ground height |
preview.jpg |
A still from the camera for thumbnails |
preflight.json |
Every preflight check at the moment you started |
capture-quality.json |
Time in each tracking state, recoveries, distance walked, top speed, peak temperature, and the coverage summary |
The PLY is deliberately local: it opens in any viewer but carries no survey coordinates. For a file a survey office can use, export a LAS.
Record scan frames
With Settings → 3D capture → Record scan frames switched on, a point-cloud capture also saves posed keyframes into the same folder. Each keyframe includes the photo, a depth map, a confidence map, the camera pose and intrinsics, and the GNSS fix nearest to it. An offline reconstruction engine can then rebuild the scan later at full quality.
- It's off by default. Frames take roughly 50–150 MB per minute.
- A frame is kept when the camera has moved at least 10 cm or turned at least 10°, and no more often than once every 0.33 seconds.
- With frames on, the preflight storage check asks for 1 GB more free space, and the timer chip shows the frame count and size as you go.
Export as LAS
- Open the capture: tap it on the Capture tab.
- Tap Export as LAS and share the file.
The LAS file is placed in your project's output coordinate system:
- It's LAS 1.2 with XYZ and RGB per point, at millimetre resolution. The project's zone is declared by its EPSG code, so survey software recognises it.
- Grid convergence at the scan's position is applied. The scan is oriented to true north, and the file is rotated to grid north.
- Heights are orthometric (MSL) where the anchor has one. Otherwise they're ellipsoidal, and the file says so.
- Each point's user data byte holds ARKit's depth confidence: 0 low, 1 medium, 2 high.
- A note inside the file records the heading and its source, the anchor's accuracy and the convergence, so
lasinfoshows where the numbers came from.
If the project has no projected coordinate system, the LAS is written on a local grid centred on the scan and isn't declared in any published zone. Set the project's coordinate system first if you need grid coordinates.