Cosine Roll-off Filter for Anomaly Profile

Use the Cosine Roll-off filter to apply a Fast-Fourier Transform Cosine Roll-off filter to the anomaly profiles.

FFT Cosine Roll-off Filter dialog options

Start roll-off (longer) wavelength	The cosine roll-off filter spreads the cut-off over a range in a smooth gradual fashion using a cosine function. This range is bound by two user specified wavelengths. Define the start wavelength of the bounding range.
End roll-off (shorter) wavelength	See above. Define the end (shorter) wavelength of the bounding range.
Degree of Filter	The higher the degree of the cosine function, the sharper the drop-off (Default is 2.0).
Low or High-Pass Filter	To filter out the noise or obtain the regional signature of the field, select Low-Pass. To obtain the near surface signature of the field, select the High-Pass option (Default is Low).

Application Notes

Ground units are the distance units defined for the model origin and projection.

The Cosine roll-off filter is commonly used for simple High-Pass or Low-Pass operations. This is because an abrupt cut-off filter causes ringing in the resulting output data. The Cosine roll-off mitigates this artifact by introducing a gradual drop over a range. The desired cut-off wavelength resides within this range, but need not be centered on the range. If you observe ringing, you can reduce the artifact by widening the separation between the short and long wavelengths, or decreasing the degree of the filter.