Use of image processing for the measurement of orientation with application to automated fish processing

The authors examine the concept of the orientation of a 2D object from three points of view; a direct axis of geometric shape, the principal axis defined in terms of the principal second movements of area, and the major axis of the fundamental ellipse fitting the boundary of the object. The three methods are implemented on a vision workstation and applied to samples of Pacific salmon. The results are compared with direct measurement orientation. The three methods of orientation measurement are evaluated quantitatively using these results, with respect to accuracy, speed of measurement and appropriateness under various practical conditions