Metrology 3D Scanners Explained: Volumetric Accuracy, Optical Tracking and Trackit SR vs Trackit

Most 3D scanners quote an accuracy such as 0.02 mm. That figure describes a single frame — one capture at close range. When you scan a 2-metre casting, hundreds of frames are joined together and small errors add up. For inspection, the number that matters is volumetric accuracy: how accurate the whole scan is across the size of the part.

What volumetric accuracy means

Volumetric accuracy is usually written as a fixed part plus a part that grows with length, for example 0.02 mm + 0.04 mm/m. Across a 1 m part the expected error is about 0.02 + 0.04 = 0.06 mm; across 2 m it is about 0.10 mm. The figure is measured under lab conditions, so allow for temperature, vibration and operator technique on the shop floor.

Acceptance tests: VDI/VDE 2634 and ISO 10360-13

A volumetric figure is only useful if you know how it was measured. VDI/VDE 2634 Part 3 is the German guideline for testing optical 3D measuring systems, and ISO 10360-13 is the international standard for optical 3D CMMs. Both measure reference artefacts — such as calibrated spheres and ball bars — placed across the measuring volume. The Revopoint Trackit SR specifies an acceptance test based on both.

Why optical tracking replaces markers

A standard handheld scanner works out its position from reference markers stuck on or around the part, and accuracy depends on how well those markers are placed. With optical tracking, a separate tracker with its own cameras follows the scanner in space. The result: no marker preparation, no marker residue on finished parts, and accuracy that does not drift as the scan grows — closer to a portable CMM than to a consumer scanner.

Revopoint Trackit SR vs Trackit

Which one should you choose?

• Choose the Trackit SR for parts up to about 4 m, when you move between machines or sites, and when you want no cable between scanner and PC. Its three laser modes cover fine detail, larger surfaces and deep holes. The CMM Edition adds a carbon-fibre ball plate for accuracy checks and a one-year Revo Measure licence for inspection reports.
• Choose the Trackit for large parts up to about 6 m — car bodies, large castings, moulds and fabricated structures — where the 11 m³ tracking volume means fewer tracker moves. It can also be integrated into automated inspection cells.

Inspection software

Revo Track (free) captures the scan. For inspection, Revo Measure compares the scan with CAD, produces colour deviation maps, GD&T checks and reports. For scan-to-CAD, export the mesh to your CAD or reverse engineering software.

Frequently asked questions

What is the difference between accuracy and volumetric accuracy?

Accuracy usually describes a single frame captured at close range. Volumetric accuracy describes the whole scan across the size of the part, written as a fixed value plus a value per metre, such as 0.02 mm + 0.04 mm/m. For inspecting medium and large parts, volumetric accuracy is the figure to compare.

Is an optical tracking 3D scanner a replacement for a CMM?

For many inspection tasks on medium and large parts it is a portable alternative to a CMM arm, with no markers and a stated volumetric accuracy. For very tight tolerances measured at a few points, a tactile CMM can still be more accurate.

Does the Trackit need markers?

No. The tracker follows the scanner optically, so parts can be scanned without markers. Markers can still be used in special cases.

Eolas Prints is an authorised Revopoint reseller and ships worldwide from Spain, with manufacturer warranty and support. See metrology & tracking 3D scanners, or send us your part size and tolerance for a recommendation.