LiDAR scanning on iPhone: the guide to mapping well

The principle: timing the light’s return

A LiDAR emits short pulses of invisible infrared light and measures how long they take to come back after hitting a surface. That time of flight gives the distance. By repeating the measurement over many points, the sensor builds a depth map of the scene.

Since it brings its own light, it measures in the dark too, which is exactly the point for underground use. Its range is a few metres: it maps what is close to you.

Which iPhones have LiDAR

LiDAR is fitted to iPhone Pro models from the iPhone 12 Pro and 12 Pro Max on, and the following Pro models. Non-Pro iPhones, and the iPhone SE, do not have it. An iPhone without LiDAR cannot build a survey with Lidark: the app says so with a “LiDAR required” message. Lidark also requires iOS 17.6 or later, and runs on iPhone only.

If in doubt about your model, look at the rear camera block: on an iPhone Pro, the LiDAR sensor is a small black disc near the lens, next to the flash.

From sensor to plan: the role of ARKit

LiDAR alone gives distances. To assemble measurements taken in different places, you must know where the iPhone was at each moment. ARKit handles this: it fuses the camera and motion sensors to track the device’s position, and rebuilds a 3D mesh of the environment.

Lidark uses this mesh: it derives an occupancy grid for the minimap and the 2D plan, a 3D view, and the way back. Everything is computed on the device, offline.

The real limits of scanning

Knowing the limits avoids disappointment:

• Range: a few metres. A very large chamber is only mapped where you pass close to the walls.
• Visual tracking: position is deduced from the camera, so a little light is needed (the torch comes on automatically) and walls with relief. A very smooth corridor, water, fog or suspended dust disturb tracking.
• Drift: over long distances, small errors can add up. The survey is indicative and does not replace a certified topographic instrument.
• Difficult surfaces: mirrors, wet surfaces and glass return infrared poorly.

Scanning a gallery well

Start the survey at the entrance. Walk slowly and smoothly, holding the iPhone at chest height and sweeping walls, ceiling and floor. Go back over missed areas rather than leaving them. If Lidark alerts you (“too fast”, “not enough detail”), stop, let tracking recover and continue: nothing is recorded while tracking is unreliable.

Back out, the survey is saved on the iPhone. In the free version you keep 3 surveys, and scanning, the minimap and the way back to the entrance always stay free. Lidark Pro (€4.99, one-time purchase) adds unlimited surveys, resume, the 3D view and PLY or OBJ export.

Battery and heat matter too: a long scan keeps the camera, the LiDAR and often the torch running at once. Start with a full battery, bring a power bank, and know that Lidark slows its saving cadence when the device heats up.

Using the result

A PLY or OBJ file opens in MeshLab, CloudCompare or Blender. You can measure, annotate, compare two visits or produce a render. You will find concrete uses in the guides to underground quarries, caving and authorised urbex, and the logic of orientation in finding your way with no GPS.

Lidark is an aid, not a guarantee: it replaces neither a guide, nor a rope, nor a prior reconnaissance. Always carry light independent of the phone, respect restricted access and read the FAQ.

A tip for exports: keep the original survey in the app and treat the PLY or OBJ as a working copy. Cleaning, decimating or aligning a mesh in desktop software never changes what Lidark stored on your iPhone.