[GRASS-user] Low pass filtering

[John Nicholls]

Hi

I am looking for some direction in applying a low pass filter to a
raster greyscale of geophysics data. The filtering objective is fairly
typical, aimed at removing influence of background noise normally
visible as linear striping or similar in a raster image created via
v.in.ascii then v.surf.idw or v.surf.bspline. I’ve tried r.mfilter
applying both 3x3 and 7x7 low pass filters as detailed in the GRASS
literature, and ask here if there are other methods either via r.mapcalc
or R which may prove more effective. I am not familiar with r.mapcalc,
nor R. I  wonder if anybody has applied lowpass filters using either of
these 2 before, and would be kind enough to provide me with a lead in to
get started. Perhaps there a manual page I've not yet got to. Still a
long way to go with GRASS, but it  really is superb for the limited
vector and raster analysis I need.

Grass version I am using is 6.4.2 on Ubuntu.

Many thanks in advance,

JohnN 

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