The accuracy of sub-pixel localisation in the canny edge detector

We examine the accuracy of the sub-pixel location of edges in the Canny de-tector using a discrete step edge model and Monte-Carlo simulation. Com-parison is made with previously published analysis in the continuous domain. In this paper we identify potential systematic errors due to a combination of the width of the smoothing kernel and the quadratic interpolation scheme which we show can be reduced to less than one-fiftieth of a pixel with look-up table. We present data which permits prediction of the likely error in the sub-pixel estimate as a function of grey level step height in the presence of noise