Disclosed is a method of, and associated apparatus for, determining an edge position relating to an edge of a feature comprised within an image, such as a scanning electron microscope image, which comprises noise. The method comprises determining a reference signal from said image; and determining said edge position with respect to said reference signal. The reference signal may be determined from the image by applying a 1-dimensional low-pass filter to the image in a direction parallel to an initial contour estimating the edge position.