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Photogrammetry

Measure a large structure with a camera

Photogrammetry turns a set of ordinary photographs into precise 3D coordinates, so deformation and shape can be measured on objects far too large for a fixed sensor.

Overview

No fixture, no rail, no power at the structure

A coordinate measuring machine needs the part to come to it. Photogrammetry works the other way round: the camera goes to the structure, and the measurement is reconstructed from the photographs afterwards.

That makes it the practical choice for large assemblies, field deployments and anything that cannot be moved, from a bridge under load to an aircraft section on the shop floor. Trilion deploys TRITOP for portable coordinate measurement and ARGUS for optical forming analysis.

How it works

Every photograph is a set of directions

A single photograph tells you the direction from the camera to each feature, but not how far away it is. Photograph the same feature from a second position and the two directions intersect at one point in space. That intersection is the measurement.

Repeat that across dozens of photographs and thousands of features, and the result is a dense set of 3D coordinates with known accuracy.

Diagram showing three photographs of a subject with feature rays converging to generate a 3D subject
Figure: NExT Lab, University of Melbourne.
Nine photographs of a cube from different angles resolving into camera positions arranged around a reconstructed wireframe model
Figure: NExT Lab, University of Melbourne.

How it works

The photographs also solve for where the camera was

The camera positions are not measured in advance. They are solved from the overlap between images: shared features seen from many angles constrain where each photograph must have been taken.

This is why coverage matters more than any single shot. Enough overlapping views, taken from varied positions, and the whole network becomes solvable.

How it works

Bundle adjustment solves everything at once

The final step refines the camera positions and the 3D point positions together, rather than one after the other. The solver adjusts the whole network until the rays from every camera agree on where each point sits, minimizing the leftover error across all of them simultaneously.

That joint solution is what turns a set of snapshots into traceable measurement, and it is where the accuracy figure on a photogrammetry report actually comes from. Scale bars and coded targets anchor the result to real units.

Two panel diagram: an initial estimate where camera rays miss each point leaving a reprojection error, and the same network after bundle adjustment where the rays intersect cleanly
Original diagram, Trilion.

Applications

Where photogrammetry is the right tool

Large structure deformation under load, alignment and as-built verification, tooling and fixture inspection, antenna and reflector shape measurement, and sheet metal forming analysis with ARGUS.

It also pairs with Digital Image Correlation on the same test: photogrammetry provides the global reference frame across a large article while DIC resolves full-field strain in the areas that matter. Common across aerospace, civil engineering and automotive programs.

Ready to measure something large?

Talk to an engineer about structure size, accuracy target and access. Not ready to buy? Rent a system or have us run the measurement on site.