Crypt, cavity, heritage: document an underground place in 3D
Updated October 5, 2026
A crypt, a vaulted cellar, a castle passage or a cavity on a historic site is fragile, poorly served by signal, and often little documented. A dated 3D survey, taken with the manager’s agreement, helps keep a record of its state. Lidark produces it with the LiDAR of an iPhone Pro, offline. It is not a certified archaeological survey: it is an archive and orientation aid, to be completed with the profession’s methods.
First, the framework: permission and conservation
Monuments, cavities and archaeological sites are, in most countries, protected and their access regulated. Enter only a place open to the public, on an organised visit, or with the written agreement of the owner or manager. Touch nothing, do not dig, do not move any object: a survey gives no right to touch the site.
Heritage associations and local authorities organise visits of places usually closed; it is often the best way to survey a site legally and safely, in the company of someone who knows it.
What a 3D survey brings
A dated 3D model can be compared with another one, months or years later. It offers:
- The real shape of vaults, pillars and niches, which a paper plan simplifies.
- A 2D plan seen from above, exportable as an image or a printable PDF (free).
- Markers dropped during the scan: inscription, crack, point of interest.
- A colour 3D model (Lidark Pro), viewable in the free web viewer, with no file upload.
How to survey a crypt or a vaulted cellar
The move is that of a gallery survey, only slower:
- Start the survey at the entrance, from the foot of the stairs or the threshold.
- Move very slowly, sweeping vaults, walls and floor, with the iPhone at chest height.
- Light evenly if you can: visual tracking benefits a lot, and the app turns the torch on by itself in the dark.
- Drop free markers to flag what matters, then finish by coming back to the entrance.
An aid, not a reference measurement
The iPhone’s LiDAR reaches about five metres with a resolution on the order of a centimetre. To document a general state, spot volumes or illustrate a file, that is useful. For an archaeological study, an architect’s survey or a listing file, it is not enough: camera tracking can drift, and nothing is georeferenced.
Present the survey as a working document, dated and indicative. Surveys taken over the years can be extended in the same frame with resume survey (Lidark Pro), but they do not replace a survey carried out by an archaeologist or a heritage architect.
Privacy and data keeping
Surveys stay on your iPhone: Lidark collects no data, has no account and uploads nothing. If you share a model, you choose with whom, through the iOS share sheet or a file.
For how LiDAR works and its limits in dark places, see the iPhone’s LiDAR and mapping a cave with an iPhone.
Frequently asked questions
Is Lidark an archaeology tool?
No. It produces an indicative 3D survey, useful as an archive and for orientation. It replaces neither the methods nor the instruments of an archaeologist or a heritage architect.
Am I allowed to survey a historic site?
It depends on the place, the country and the owner. Many sites are protected and their access regulated. Survey only with the manager’s permission or on an organised visit, and touch nothing.
What accuracy for a crypt model?
On the order of a centimetre locally with a reach of about five metres, but drifts can build up and nothing is georeferenced. No certified accuracy is promised.
Can I compare two surveys a year apart?
You can resume an existing survey to extend it in the same frame (Lidark Pro). There is no automatic comparison tool between two surveys.
Do I need a special iPhone?
Yes: an iPhone Pro with a LiDAR scanner (iPhone 12 Pro and later Pro models). Without LiDAR you cannot scan.