The LiDAR scanner on Pro iPhones and iPad Pros works like sonar, but with light: it fires pulses of infrared light and times how long each takes to bounce back. Thousands of times per second, in a grid across the room.
From points to walls
Raw LiDAR gives you a point cloud — millions of tiny distance measurements. That's not a floor plan. Scanstead runs Apple's RoomPlan understanding on top, which recognizes the structure in those points: this flat region is a wall, this rectangle in it is a window, this gap is a doorway.
That distinction matters for accuracy. A point cloud can tell you a surface is about 12 feet away. A recognized wall is a plane fitted across thousands of points, which averages out the noise. That's how a phone gets to inch-level dimensions on typical rooms.
What affects accuracy
A few practical things move the needle:
- Walk, don't wave. A steady pace gives the sensor overlapping views of every surface.
- Corners are anchors. Give each corner a second of attention; corners lock the geometry.
- Glass and mirrors lie. LiDAR pulses go through glass and bounce off mirrors. Scanstead's structural model handles most of it, but keep an eye on mirrored closets.
- Light doesn't matter. LiDAR brings its own light — dim basements scan as well as sunny kitchens.
The part you never see
After the scan, Scanstead extracts measurements from the structural model: wall lengths and heights, opening dimensions, floor area, perimeter. Shared walls between rooms are deduplicated so a whole-house scan doesn't double-count the wall between the kitchen and the dining room.
You walk. The phone does the math.