Compared to the moment-preserving technique, the approach based on the expectation of first-order derivatives can solve the problem of multiresponse (misdetection of several edges). One comparison of these two techniques is given in Table 2.3. For some similar sequences, the subpixel-level location for the expectation technique is less sensitive to the length of the input sequence.

Using Tangent Direction Information: Both of the above methods detect the subpixel-level edges using the statistical property of the blurred boundary that has a certain width, so the edge location can be determined using the information along the normal direction to the boundary. In cases where the boundary ramp is sharp, there would be few boundary pixels used ...

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