Butterworth Notch (BTWRN)

Use the Butterworth Notch option to apply a Butterworth Notch filter.

Butterworth Notch Filter dialog options

Wavelength cutoff	Central wavelength to be rejected, in ground units.
Filter order	The order n of the filter, which controls the sharpness of the notch. Default is 8.

Application Notes

The Butterworth Notch filter rejects a selected mid‑wavenumber range while preserving both the low and high extremes of the wavenumber spectrum. The Filter order controls how sharply the filter attenuates the selected wavenumber region: higher values produce a steeper transition at the cutoff boundaries.

Butterworth Notch Filter

Where:

kc	Wavenumber cutoff (cycles per ground unit).
n	Positive integer determining the sharpness of the cutoff.

Wavenumber Domain Variable Definitions

The following variables are used in the wavenumber domain:
k	Wavenumber increment, used to depict a radially symmetrical variable.	Where: np: number of points cs: cell size
μ	X-component of the wavenumber.
v	Y-component of the wavenumber.
r	Radial component of the wavenumber.
θ	Angular (polar) component of the wavenumber.

Ground unit refers to the survey ground units defined in your grid (e.g., metres or feet). Ground units may be left undefined.