Underground quarry plan: survey galleries with an iPhone Pro

A real need, a complementary tool

A quarry plan serves staff safety, monitoring of voids, access management and site documentation. Reference surveys are made with total stations, terrestrial laser scanners or dedicated surveys, by professionals. These tools are accurate, but heavy, slow to set up and costly for a simple overview.

Lidark aims at the other end: a reconnaissance survey in a few minutes, with the phone already in your pocket. It does not claim to be a certified measuring instrument. For regulatory use, validate dimensions with your own means.

Typical uses include a first reconnaissance before a full survey, documenting a sector that was never planned, checking how a route connects two known points, and keeping a visual record of a gallery’s condition from one visit to the next. In each case the value lies in speed and in the habit of recording: a rough but dated 3D model beats a precise plan that was never made.

What a survey produces

After a scan, you have several views of the same survey:

• 2D plan of the gallery: walls, walkable floor coloured by altitude, the walked path and the landmarks you dropped.
• Altitude profile: total development in metres, lowest point relative to the entrance, useful to spot ramps, shafts and levels.
• 3D “dollhouse” view, ceilings removed, to understand the volume and height of galleries (Lidark Pro).
• PLY and OBJ export, with or without altitude colours, to carry on in CloudCompare, MeshLab, Blender or CAD software (Lidark Pro).

Method for a good survey

The iPhone’s LiDAR measures a few metres out and position tracking is visual: survey quality therefore depends on how you walk. Start the survey at the entrance so everything is referenced to it. Walk slowly and smoothly, sweeping walls and ceiling, not just the floor. Keep the torch on: it switches on automatically in the dark, and tracking needs it.

In a pillar quarry, pass through junctions again: a path that forms a loop helps Lidark shorten the way back. Drop a landmark at each notable point: shaft, rockfall, sign, change of level. If you get a “too fast” or “not enough detail” alert, stop, slow down, light a wall with more relief, then continue.

Plan your survey like a walk with a purpose. Decide the main axis first, then the side galleries, and finish by closing loops where you can. Take a minute at the entrance to check that the torch works, that the battery is full and that storage is not nearly empty, since a survey grows with every gallery you add.

Coming back to complete a survey

A quarry is not always surveyed in one go. Resuming a survey (Lidark Pro) lets you come back, walk into an already scanned area and extend the rest in the same frame. Lidark first tries ARKit’s visual relocalization, then a shape-based alignment on the walls, which does not depend on light: underground, two pictures of the same wall never look alike.

Safety and responsibilities

A quarry can be unstable: falling blocks, voids, water, bad air. Access is up to the owner or operator, and work must follow their rules with suitable equipment. Lidark replaces neither a guide, nor a rope, nor a prior reconnaissance, and must never be used to justify entering a forbidden site.

Always carry light independent of the phone, tell someone your return time and work as a team. More in the FAQ.

Data: everything stays on the device

For sometimes sensitive site data, one detail matters: Lidark works offline, with no account and no server. Surveys are stored on the iPhone, and only leave it if you export and share a file yourself. Details are in the privacy policy. To find your way without a network, see also the underground map with no GPS.