Cosine Roll-off (COSN)
Use the Cosine Roll-off option to apply a cosine roll-off filter.
Cosine Roll-off Filter dialog options
Long wavelength cutoff |
The starting wavelength roll-off in ground unit. See illustration, this parameter is equivalent to k0-1. |
Short wavelength cutoff |
The ending wavelength roll-off in ground unit. See illustration, this parameter is equivalent to k1-1. |
The degree n of the cosine function. The higher the degree, the sharper the roll-off. The default is 2. |
|
Low pass or High pass |
To generate the regional field, select Low pass. This is the default. The High pass is the reciprocal filter and produces the residual field. |
Application Notes
Because this filter has a smooth shape, and it does not alter the energy spectrum below the start of roll-off (or after the end of roll-off in high-pass mode), it is commonly used for simple high-pass or low-pass operations. To reduce ringing, the separation between k1 and k0 can be increased.
Cosine roll-off filter
Where,
k0 |
The starting wavelength roll-off. |
k1 |
The ending wavelength roll-off. |
n |
Positive integer value determining the degree of sharpness of the cutoff. |
k |
Wavenumber domain increment, used to depict a radially symmetrical variable. |
where: np is the number of points cs is the cell size |
u |
X component in the wavenumber domain. | k = 2π ( i μ+j ν ) |
v |
Y component in the wavenumber domain. |
|
r |
Radial component in the wavenumber domain. |
also 2πk |
θ |
Polar component in the wavenumber domain. |
|
Ground_unit is the survey ground units as defined in your grid (e.g. metre or feet). Ground units may be left undefined.
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