Apply Single FFT Filter
Use the Apply Single FFT Filter option (geogxnet.dll(Geosoft.GX.FFT1D.FFT1DFiltering;RunGravityFilters)*) from the menu Moving Platform Gravity > Filters to apply a single 1D Fast-Fourier Transform filter to a channel.
Apply Single FFT Filter dialog options
Channel to filter |
Name of the input channel to filter. Script Parameter: FFT1MULT.IN |
Output channel |
Name of the output channel (created if does not exist). Script Parameter: FFT1MULT.OUT |
Filter to apply |
Select the filter name to apply. The selected filter's parameters will be displayed below. The filter parameters displayed will be different depending on the filter selected. The following filters can be selected:
Script Parameter: FFT1MULT.FILTER |
More |
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Distance increment |
Specify the distance increment in ground units. If not specified, the nominal data spacing will be used. Script Parameter: FFT1MULT.SAMPINCR |
Interpolation method |
Select the Interpolation method to be used as, Minimum Curvature, Linear, or Akima. Script Parameter: FFT1MULT.METHOD |
Application Notes
*The GX tool will search in the "...\Geosoft\Desktop Applications \gx" folder. The GX.Net tools, however, are embedded in the geogxnet.dll located in the "...\Geosoft\Desktop Applications \bin" folder. If running this GX interactively, bypassing the menu, first change the folder to point to the "bin" folder, then supply the GX.Net tool in the specified format.
The dialog enables a single filter to be applied to a channel with a single process, in which, the data first gets Fourier Transformed (FT) to the wavenumber domain, then the filter is applied, and the data finally are Inverse Fourier Transformed (IFT) back to the space domain.
The FFT sampling parameters (Distance increment and Interpolation method) ensure that the input data is appropriately sampled for 1D FFT. If your data has a variable spacing between samples (such as may occur in ground-based surveys) then the default Minimum Curvature interpolation method may result in the introduction of artifacts into the filtered output. If this occurs, changing the interpolation method to "Linear", or specifying a distance increment that is appropriate to your data will likely prevent those artifacts from occurring.
The relevant parameters for the selected filter will be displayed, prompting you to enter the values.
Finding Help for a Specific Filter
Once you have selected your filter in the Apply Single Filter dialog, click the Help button and the information for your selected filter will be displayed. You can also click the filter links below.
See Also:
- Apply Multiple Filters
- Apparent Density Filter
- Apparent Susceptibility Filter
- Bandpass Filter
- Butterworth Filter
- Continuation Filter
- Cosine Roll-off Filter
- Gaussian Filter
- High-Pass Filter
- Horizontal Derivative Filter
- Horizontal Integration Filter
- Low-Pass Filter
- Resistance Capacitance Filter
- Reduce to Magnetic Pole Filter
- Vertical Derivative Filter
- Vertical Integration Filter
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