Polycam alternative: scanning a cave or an authorised tunnel

What general-purpose scanners do very well

Polycam captures with LiDAR and photogrammetry, and offers an editor, a web version and several export formats. Scaniverse processes on the device, with fast capture and simple sharing. To digitise a room, an object or a facade, they are mature, feature-rich and well documented. Free and paid features change: check the App Store.

If your goal is a textured model to share online, a photorealistic result or a detailed object, stay with a general-purpose app. Lidark does not try to replace them there, and it would be dishonest to claim otherwise.

What changes underground

A cave, a quarry or an authorised mine bring constraints that room scanners do not have to handle:

• No GPS or network: every position is relative to the entrance, and an app that depends on the cloud or an online map is useless.
• Total darkness: LiDAR measures without light, but position tracking is visual and needs lighting. Your screen must not ruin your night vision either.
• A route, not a volume: you move along a line, fork, loop. You need a map that builds itself live, not a model you look at afterwards.
• The way back: knowing at every moment the real distance to the exit along the path already walked, not as the crow flies through the rock.
• Gloved hands, mud, battery: large buttons, a sober screen, controlled power use.

What Lidark adds

Lidark was designed for these five constraints, and only for them. A live minimap shows walls, walkable floor and path. The thread back computes the real return distance and points to the next stretch, with a shortcut when the path loops. Landmarks (junction, shaft, danger) drop in one tap. Night vision turns the screen and camera red. Everything works offline, with no account.

Back at the surface, the survey opens as a 2D plan and altitude profile, and with Lidark Pro as a 3D view with the ceilings removed and as a PLY or OBJ export. The orientation principle is detailed in finding your way without GPS or network.

What Lidark does not do

Honesty is part of a comparison. Choose a general-purpose app if any of these points is decisive for you:

• No photo textures: Lidark keeps no photo or video, only a mesh and altitude colours.
• No photogrammetry, no cloud processing and no built-in online sharing.
• No georeferencing: the frame is local, centred on the entrance.
• iPhone Pro with LiDAR only, about 5 metres of range, and visual tracking that suffers on very smooth surfaces, water and dust.
• An indicative survey, not a certified surveying instrument.

When to use which

A simple grid, with no tribalism:

• Digitising a cellar, a shelter or a room visited with a guide, for the archive: a general-purpose app may be enough, especially if you want textures.
• Walking a gallery with no landmarks, and having to get back out: Lidark, for the minimap and the way back.
• Surveying an authorised quarry or cave alongside traditional survey: Lidark for the path and the volume, your instruments for the dimensions.
• An object, a facade, an interior: a general-purpose or photogrammetry app.

A concrete example

Take an old pillar-and-room quarry, visited with the operator’s agreement. With a room scanner you end up with a nice model, but during the visit the app does not tell you which direction the exit is in, or how many metres away it is. With Lidark, the minimap draws itself as you advance, a landmark marks each junction, and the return arrow points at the next stretch of the path already walked.

Conversely, if the same operator asks you for a textured, shareable model for a presentation, a general-purpose app will serve best. Both needs are real; they do not compete.

Combine them rather than choose

Nothing obliges you to keep only one. A sensible explorer can use Lidark to find their way during the visit, then open the exported PLY or OBJ in MeshLab, CloudCompare or Blender, or simply in the free 3D viewer, which reads the file locally. The guide to 3D scanner apps details the choice by use.

Safety and the legal framework

Whatever the app, a map is not a guarantee. Lidark replaces neither a guide, nor a rope, nor a prior reconnaissance. Enter only where you have permission, carry two light sources independent of the phone and tell someone your return time. For practice, read mapping a cave with an iPhone, and find every guide on the guides page.

Frequently asked questions