[GRASS-dev] r.resamp.filter - Resamples raster map layers using an analytic kernel - how to use gauss filter?

[Helmut Kudrnovsky]

Hi,

I'm trying to follow/understand the calculation/algorithm of a
multiresolution index of valley bottom flatness [1] transcribed to GRASS
GIS.

"The remaining steps are similar to the second step.
The main differences are that the DEM is smoothed, the
resolution becomes coarser at each step, and the combined
flatness from previous steps is included to prevent fine-scale
nonflat areas being lost in the coarser-scale analysis." 
[...]
First, a smoothed DEM (DEML,L,L-1) is derived
without changing resolution. The smoothing is performed
with the Arc/Info 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?	

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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