harmonica.filters.derivative_upward_kernel(fft_grid, order=1)[source]

Filter for upward derivative in frequency domain

Return a xarray.DataArray with the values of the frequency domain filter for computing the upward derivative. The filter is built upon the frequency coordinates of the passed fft_grid and is defined as follows:

\[g(\mathbf{k}) = |\mathbf{k}| ^ n\]

where \(\mathbf{k}\) is the wavenumber vector (\(\mathbf{k} = 2\pi \mathbf{f}\) where \(\mathbf{f}\) is the frequency vector) and \(n\) is the order of the derivative.

  • fft_grid (xarray.DataArray) – Array with the Fourier transform of the original grid. Its dimensions should be in the following order: freq_northing, freq_easting. Use xrft.xrft.fft and xrft.xrft.ifft functions to compute the Fourier Transform and its inverse, respectively.

  • order (int) – The order of the derivative. Default to 1.


da_filter (xarray.DataArray) – Array with the kernel for the upward derivative filter in frequency domain.