Direct orthogonal signal correction

In the present paper, the concept of orthogonal signal correction (OSC) as a spectral preprocessing method is discussed and a number of OSC algorithms that have appeared are compared from a theoretical viewpoint. Since all of these algorithms had some problems concerning the orthogonality towards Y, non-optimal amount of variance removed from X, or a non-attainable solution, a new direct OSC algorithm (DOSC) is introduced. DOSC was originally developed as a direct method solely based on least squares steps that had none of the problems mentioned above. The first practical results with the new method, however, were not encouraging due to the complete orthogonality constraint. If this orthogonality constraint is loosened, the method improves considerably and simplifies the calibration model for the prediction of Y.