3D Scanning and Metrology

A scan is a measurement, and like every measurement it needs an error budget. This note describes how we build one for the three instrument classes we use most: structured light scanners, laser trackers and photogrammetry from calibrated cameras.

Building an error budget

Start from the instrument specification, then add the contributions that the specification does not cover: fixturing, thermal drift, surface finish and the registration of multiple scan positions. In our experience registration is the largest single term on objects longer than two metres.

Verification

Never accept a scan without a reference artefact in the same field of view. A simple calibrated sphere or step gauge captured alongside the part turns an unverifiable point cloud into a traceable measurement.