ReVisit
Revisit the survey's viewpoint. Return to a site with a phone, and see it as it was.
Garni, Armenia: the bathhouse mosaic, two years on
Survey · 30 October 2024
Today · 6 October 2026
Drag the curtain. Left, the digital twin of the 2024 survey, rendered from the phone's viewpoint. Right, the photograph taken with the phone in 2026. Between the two, restoration has begun: the lacunae have been filled with gravel and protected, the tesserae cleaned. ReVisit does not say so: it shows it.
The idea in a few lines
A site has been surveyed. Months or years later, the archaeologist or the conservator comes back with a simple phone and aims at the structure. ReVisit recognises the viewpoint and presents the site as it was on the day of the survey, seen from exactly the same spot.
They then hold two strictly comparable images: the state of reference and today's state. A lacuna that has spread, a lost tessera, an open crack, a restoration: the expert eye judges, on documents that can at last be superposed.
Come back and see.
What Garni taught us
The survey
On 30 October 2024 the bathhouse floor mosaic is surveyed in situ: 430 photographs, 36 targets measured with a total station. That survey becomes the digital twin, the dated state of reference.
The return
On 6 and 8 October 2026 the team comes back and photographs the floor with a phone, hand-held, in a few minutes. For each photograph, ReVisit renders the 2024 image seen from the same spot.
The lesson
When a site has changed a great deal, the old survey is no longer enough to relocalise everywhere. A few views from the visit itself, added to the twin, restore it. The twin thus stays up to date, visit after visit.
Relocalisation computed after the mission, the 2024 twin being completed with views taken two days later. With the 2024 survey alone: 8 photographs out of 29.
The floor mosaic of the Garni bathhouse, 3rd century AD, is being restored within the ARC-HE-TOUR-DEV project, coordinated by the University of Florence in collaboration with ISMEO and the Opificio delle Pietre Dure, and funded by the Italian Agency for Development Cooperation.
Alleins, Provence: the Saint-Pierre chapel
The chapel was surveyed in October 2026: two twins, the west facade and the north-east corner, 331 and 400 photographs. A few days later, ReVisit relocalises a phone's photographs to within 3.6 mm on the stone (north-east corner, 107 photographs) and presents the survey and today's state in the chosen mode.
Two versions, one site
A light version, Android and iOS. Aim, compare on the spot, with no network.
- Curtain, side by side, top and bottom
- The site loads with a code, then everything works offline
Mac or Windows. Go back over the visit at leisure, on a large screen.
- A whole folder of photographs relocalised in one go
- A report of each visit, to archive
Today ReVisit guarantees the viewpoint and leaves the judgement to the expert: it makes no diagnosis. In the near future will come automatic detection of the areas that have changed and their measurement in 2D, which the expert confirms or dismisses.
How it works
- A digital twin of the site, built by photogrammetry and laser scanning. It fixes the state of reference at the date of the survey.
- An application that computes, in the phone, its position and orientation relative to that twin.
- A virtual camera identical to the phone's, which renders the twin from that viewpoint.
The viewpoint is free: the reference image is produced for any position, not only those of the survey. No infrastructure on site: no targets, no beacons, no network.
Protected sites. One application, the same for everyone. Each site is a distinct data package, opened with a code handed to its holder; no monument and no survey data is in the application itself.
ReVisit Studio at Garni, the film
Seven iPhone images of 8 October 2026, with no position data at all, are dropped into ReVisit Studio. Each one finds its place in the survey of 30 October 2024: in the 3D model, then on the plan of the site.
Half the film is the comparison: on the left the survey, on the right the photograph, and between the two a figure and a Greek inscription that have come out of the ground.
Screen capture of the application. The title cards are in Italian, the language of the project team.
Who it can serve
- Building archaeology: monitoring of facings, masonries and weakened zones between two campaigns; documentation of interventions.
- Conservation and restoration: surveillance of surface alterations, spalling, structural disorders; quick comparative condition report, without a new survey campaign.
- Civil engineering and structures: periodic visual inspection of piers, vaults and retaining walls, with immediate return to the state of reference.
- Caves and confined sites: return to the exact viewpoint in environments where every measurement is costly.
What it takes to start
- A survey of the site, existing or to be carried out. image4D can take it on or rely on a survey provided.
- An ordinary Android or iOS phone for consultation on site.
- A domain contact to define the zones to monitor and assess the real usefulness of the image pairs.