Figure 8. Appearance of the scanned image of the record and the outcome of automatic trace following for different choices of threshold level. This example corresponds to an image scanned at 600 dpi resolution with 256 level gray scale. Notice the spurious peak in the digitized data due to noise in the scanned image for lower threshold level (190). For higher threshold levels (e.g., 230), the trace image becomes discontinuous. For clarity, the horizontal scale is stretched three times relative to the vertical.