Hi Lester, The spatial resolution of 0.016 m seems unrealistically too-finely sampled... Could you confirm the units? Also, it is possible that your upward continuation requires an angular wavenumber: exp(-2*%pi*k*uc) ?
Regards, Rafael -----Original Message----- From: users <[email protected]> On Behalf Of arctica1963 Sent: Saturday, July 28, 2018 2:23 PM To: [email protected] Subject: Re: [Scilab-users] FFT - upward continuation of a 2D grid Hi Rafael, Thanks for the pointers. Still having some issues getting it to work on real data. Upward continuation, should act like a low-pass and give a smoother view of the data. dimx=size(xt); dimy=size(yt); nx=dimx(1); ny=dimy(1); dxy = 0.016666666; dkx=1/(nx*dxy); dky=1/(ny*dxy); kx=dkx*(-(nx/2)+1:nx/2); ky=dky*(-(ny/2)+1:ny/2); [KX,KY]=meshgrid(kx,ky); k=sqrt(KX.^2 + KY.^2); uc=4000; // continue up 4000m //fft_Boug_corr=fft2(Boug_corr); //shift_f=fftshift(fft_Boug_corr); //fft_clean=clean(shift_f); fft_clean=clean(fftshift(fft2(Boug_corr))); // merge commands Fup=fft_clean.*exp(-k*uc); F_real=real(ifft(Fup)); It does generate output, but certainly not as expected for upward continuation of data. Not sure what I'm missing, assuming I have done the wavenumber thing correct. Normally I would do this via GMT, but want to get it going under Scilab for convenience. Clearly, before doing a proper fft, we need to pad the data to expand the dimensions over which the fft is done to avoid edge effects. Just running it with the grid dimensions should still produce a recognisable result. Matbe testing with a synthetic grid would help. Cheers Lester -- Sent from: http://mailinglists.scilab.org/Scilab-users-Mailing-Lists-Archives-f2602246.html _______________________________________________ users mailing list [email protected] http://lists.scilab.org/mailman/listinfo/users _______________________________________________ users mailing list [email protected] http://lists.scilab.org/mailman/listinfo/users
