Flatness measurement requires the measured object, the sensors or both to be moved.

For a multi-track flatness measurement, an object is transported through below the sensor system. The number of tracks limits what errors may be detected.

A complete surface check requires a camera system. The camera may be supported by a laser line, projected perpendicular to the transport direction. Surface errors like gaps, fissures, dents or bumps are detected by the deformation they cause in the laser line.