Butterworth Filter

Use the Butterworth option to apply a Fast-Fourier Transform Butterworth 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

Butterworth filter options

Central Wavelength cutoff (in ground units)

Central Wavelength cutoff value, in ground units (Default 1)

Script Parameter: FFTBUTTW.WAVEL

Degree of Filter

Degree of the Filter function (default = 8)

Script Parameter: FFTBUTTW.DEGREE

Low or High Pass Filter

Low or High Pass filter (default = Low)

Script Parameter: FFTBUTTW.PASS

Application Notes

The Butterworth filter is excellent for applying straight forward high-pass and low-pass filters to data because you can easily control the degree of filter roll-off while leaving the central wavenumber fixed. If ringing is observed, the degree can be reduced until acceptable. A common, but more complicated alternative is the Cosine Filter).

Butterworth Filter

image\ebx_82254035.jpg

image\ebx_-704529198.jpg

Parameters:
k0 

Central wavenumber of the filter.

n Degree of the Butterworth filter function. By default, we assume a degree of 8.
0/1

Residual/Regional flag to specify if a residual high pass or a regional low pass is required. By default, the system applies a regional filter.