[GRASS-user] Median filtering time series in time only

nik at nikosalexandris.net nik at nikosalexandris.net
Wed Jan 27 03:37:15 PST 2021


I am trying to median-filter time series in time and not in space.

Not sure `r.series.filter` is the right tool.
I skimmed through the manual, the paper and the source code. Yet I am 
asking for a confirmation.
Its (odd integer) parameter `winsize=` implies a moving window (of size 
winsize^2).
Does this rather filter images, of a time series, in space?
Or does the `winsize` here refer to the length of a moving temporal 
window?

Then, there is `r.series.lwr`.
Can I use the tool with `order=0` and `delta=1` (or `order=3` and 
`delta=1`)
and perform a moving average filtering in time?
It's not median. Still I'd like to see a filtering in time-only effect.

And, now I recall `r.hants`.
Is there a way to use it for filtering-out only lows and highs (`-l` and 
`-h` respectively) pixel-wise in time, without interpolating nor 
extrapolating?

Else, I guess there should be a way to build a 'custom' filter using 
`t.rast.algebra` using its temporal neighborhood modifier.
It's convenient if one the tools above does already median-filtering in 
time-only.

Kind regards, Nikos


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