Left: idealistic example of the edge detection method using a synthetic circumstellar disk with added Gaussian background noise. The radial cuts (dashed white lines) sample intensity profiles iteratively. Magenta dots mark detected disk edges where intensity first (measured inwards towards the star) exceeds a 5σ noise primary threshold and passes the step function criteria. Edge labels are shown only on the right side of the disk (angles between 0° and 180° clockwise) for clarity. Background noise level (σ) and primary threshold (5σ) are annotated in the figure. Right: radial intensity profile extracted at 180° from the centre of GM Aur in H-band, comparing the real high-S/N case (blue) and a synthetically degraded low-S/N case (orange). Horizontal dashed lines indicate the 5σ and 3σ primary thresholds used for edge detection. Step points used to confirm edge detection are marked with red crosses, and the final detected edge locations are indicated by vertical dashed-dotted lines and filled circles. The low-S/N profile shows degraded detection performance and premature truncation due to the outer edge being buried in noise.