[GRASS-user] Question about MODIS band 5 destriping?
glynn at gclements.plus.com
Wed Apr 9 23:09:50 EDT 2008
Markus Neteler wrote:
> > > I think that the strange i.fft file format is an obstacle here. AFAIK it
> > > is not saved as "normal" raster file which limits the possibilities to
> > > elaborate. Maybe I am wrong, don't quite remember well..
> > No, you're quite correct.
> > i.ifft ignores the actual input map, reading the data from the fftreal
> > and fftimag files created by i.ifft. So you can't modify the i.fft
> > output with e.g. r.mapcalc than use i.ifft on the result. The only
> > modification which can be performed on the FFT data is masking; i.ifft
> > reads the mask separately and applies it to the data.
> Could we change this for GRASS 7? Possibly there was a reason
> to implement it as private solution but hopefullyx we can work around
The main issue is that you can't store both the real and imaginary
components (or, alternatively, magnitude and phase) in a single map.
The other issues (e.g. the fact that an array of FFT coefficients
isn't actually geodata) can probably be fudged around.
Glynn Clements <glynn at gclements.plus.com>
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