Abstract: A method and apparatus for automating the measurement of straightness of linear stock material produced by the operation of a mill. As the linear stock material exits from the mill, sensors acquire a sequence of image or distance measurement pairs associated with the material at discrete longitudinal points over a segment of the material. A processing system utilizes the data pairs to determine a set of centroids for a segment of the material. A virtual axis is identified between centroids associated with the segment, and the processing system determines a measure of deviation of each remaining centroid in a segment from the virtual axis to identify a degree of concavity of the material within the segment, as well as to identify a measure of the angular orientation of the concavity about the virtual axis.