[GRASS-user] focal mean function using an 11 x 11 Gaussian smoothing kernel g(r) with an effective radius of three cells?

[Helmut Kudrnovsky]

hi,

I'm trying to understand the calculation/algorithm of a
multiresolution index of valley bottom flatness [1] in order to port it
to GRASS GIS.

"The smoothing is performed
with the focal mean function using an 11 x 11
Gaussian smoothing kernel g(r) with an effective radius of
three cells (to correspond with the factor of 3 resolution
change):

    g(r) = 4.3565e -(r/3)2       [x to the power of n]

where r is the distance (in cells) from the center of the
kernel." [1]

would there be r.resamp.filter [2] using a gauss filter the appropriate
tool?

maybe with?: 

r.resamp.filter

radius= 3
    Filter radius
x_radius = 11
    Filter radius (horizontal)
y_radius= 11
    Filter radius (vertical)

but also in r.neighbors [3] there is a gauss option

gauss=float
    Sigma (in cells) for Gaussian filter


any hints/pointers out there?

thanks
Helmut


[1] John C. Gallant and Trevor I. Dowling 2003. A multiresolution index of
valley bottom flatness for mapping depositional areas. WATER RESOURCES
RESEARCH, VOL. 39, NO. 12, 1347, doi:10.1029/2002WR001426, 2003
[2] http://grass.osgeo.org/grass71/manuals/r.resamp.filter.html
[3] http://grass.osgeo.org/grass71/manuals/r.neighbors.html




-----
best regards
Helmut
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