Low-pass Filter

Use the Low-pass option to apply a Fast-Fourier Transform Low-pass filter to a channel.

The filter option is available with the following extensions and menus:

Geophysics: 1D FFT > 1D Filtering
Gravity and Terrain Correction: Moving Platform Gravity > Apply Single FFT Filter

Wavelength cutoff
(in ground units)

Wavelength cutoff value, in ground units (Default is 1).

Script Parameter: FFTLOWP.WAVEL

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L(k) = 1, for k £ k0
L(k) = 0, for k > k0

k₀ The cutoff wavenumber in cycles/ground_unit. All wavenumbers above this value are removed.

Ground_unit is the survey ground units used in your grid (e.g. metre, feet etc.).

As with the band-pass filter, the low-pass filter is seldom used because the results usually suffer from Gibb's Phenomena (ringing).