Low-pass (LPAS)

Use the Low-pass option to apply a low-pass filter to the data.

Low-pass Filter dialog options

Cutoff wavelength

The cutoff wavelength, k0-1, in ground units. All wavelengths shorter than this value are removed.

Application Notes

A low-pass filter can be used to pass or reject specific wavelength ranges within the data. However, applying a simple cutoff filter to an energy spectrum almost invariably introduces a significant amount of oscillation — commonly known as Gibbs’ Phenomenon. This filter is provided for completeness, but for most applications we recommend using a tapered filter such as the Butterworth filter (BTWR), which produces smoother results.

Low-pass operator

L(k) = 1	for k ≤ k0
L(k) = 0	for k > k0

Where:

k = wavenumber

k₀ = cutoff wavenumber

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.