A carved stone can now be recorded down to its finest grooves without anyone touching it.
Museums and archaeologists use photogrammetry to turn ordinary overlapping photographs into accurate 3D models of sculpture, rock art and objects. This independent guide explains, from museum and university sources, how it works, where it struggles, and how it helped record a buried Neolithic carving near Glasgow.
AI-generated image, not a photograph of a real person or place.
CAPTURE every angle
Overlap every photo
Matte beats shiny
Scale bars for accuracy
Old surfaces, new records
THE SHORT ANSWER
Many photos, one model.
Software finds the same points in different photographs. From those, it builds a cloud of points, then a surface.
HOW IT WORKS
Overlapping photographs
Photogrammetry uses hundreds of overlapping photographs taken from many angles. Software spots common features across images, plots them as a point cloud and joins them into a mesh.
The Cleveland Museum of Art photographs objects on turntables, using calibrated scale bars accurate to a tenth of a millimetre or better, and polarised light to stop reflections confusing the software.
In 2016 the Cochno Stone near Glasgow, a Neolithic cup-and-ring panel buried since 1965, was uncovered for two weeks, recorded in 3D and reburied to protect it.
Pick a kind of object to see what museum specialists say about recording it with photogrammetry. The bar shows how difficult it tends to be.
Based on comments from the Museums Association, the Cleveland Museum of Art and Factum Foundation. Results depend on skill, equipment and conditions.
TWO NUMBERS WORTH KNOWING
How big, and how precise.
One measurement from a Scottish hillside, one from a museum photo studio.
8 × 13 m
Size of the carved rock panel
Dating to about 3000 BC and called the most important Neolithic cup-and-ring marked panel in Europe, it was recorded by the University of Glasgow and Factum Foundation in 2016, then reburied.
THE COCHNO STONE · UNIVERSITY OF GLASGOW
0.1 mm
Scale-bar accuracy in its method
Individually calibrated scale bars accurate to a tenth of a millimetre or better mean the finished models are accurate to that level and look like the real objects.
ACCURACY · CLEVELAND MUSEUM OF ART
For a sense of scale on the data side: a 3D model of the picture room at Sir John Soane's Museum in London used about 5,000 photographs, according to the Museums Association.
FOUR STEPS TO A MODEL
From camera to mesh.
This is the general workflow described by Factum Foundation and the Cleveland Museum of Art.
Photograph every part, several times
Take a series of overlapping photographs so every part of the object appears in several images, from many angles.
Let software find common points
The software identifies the same surface features across images and works out where each camera was.
Build the point cloud
Each matched feature becomes a point with x, y and z coordinates. Together they form a point cloud.
Make and clean the mesh
Points are triangulated into a mesh of vertices, edges and flat planes, coloured from the photos, then cleaned up by a specialist.
AI-generated image, not a photograph of a real person or place.
PHOTOGRAMMETRY OR LASER SCANNING?
Shape and colour together.
AI-generated image, not a photograph of a real person or place.
Laser scanning can produce accurate 3D models, but the Cleveland Museum of Art notes they come out with a blank surface appearance. Photogrammetry captures shape and photographic texture together, and Factum Foundation sometimes combines it with white-light or LiDAR data.
It is also, in Factum's words, a fundamentally democratic technology: anyone with a phone camera and free software can try it. High-resolution results still take skill in both photography and processing, and storing the large amount of data is a real cost for museums.
Questions
Questions people ask
What is photogrammetry?
A 3D recording technique that uses many overlapping 2D photographs of an object, taken from different angles, and software that matches common points to build a 3D model.
Is photogrammetry better than laser scanning?
Each has strengths. The Cleveland Museum of Art says laser scanning can be accurate but gives a blank surface appearance, while photogrammetry records shape and photographic texture together.
What objects are hard to record?
Museum specialists say shiny surfaces such as glass or varnished wood and very thin objects are difficult. Polarised light and dark backgrounds can help with reflections.
What was the Cochno Stone project?
In 2016 the University of Glasgow and Factum Foundation uncovered the Cochno Stone, an 8 m by 13 m Neolithic rock art panel near Clydebank buried since 1965, recorded it in 3D during a two-week excavation and reburied it.
Can I try photogrammetry at home?
Factum Foundation says it can be done by anyone with a phone camera and free software, though high-resolution, accurate models need skill, good equipment and many well-overlapped images.
