Abstract. Non-contact sensors are becoming an increasingly popular tool for use in dimensional measurement, inspection and quality control. However, there exist a number of challenges associated with the use of these non-contact sensors in dimensional inspection systems. One important challenge is to understand the associated measurement errors and determine the objective accuracy of such an inspection system. This paper examines the effect of misalignment and scanning methodology on the measurement accuracy of a non-contact dimensional inspection system. It is important to understand this topic since the majority of optical sensor manufacturers do not supply information about the alignment between the optical line of sight and the mechanical interface of the sensor or measurement system. We prove the evidence of this measurement error through both experimental results and simulation. Finally, by using a constant standoff measurement method we succeeded to show that the majority of inherent misalignment error can be eliminated.