[GRASSLIST:8504] Re: neighbourhood analysis

[Robert Nuske]

Ksenia Konwicki wrote:
> Hello,
>
> I am trying to do landform analysis based on various elevational
> variability charateristics. I wanted to used a circular focal point
> moving window analysis. My DEM is 30m resolution. I am currently running
> Grass 6.0 through Cygwin.
>
> I have tried using r.neighbours but it seems to limit my window size to
> 25 pixels (750m), and what I can see only offers a square neighbourhood.
> I would like to do my analysis over a 3000m area so I need a much larger
> window. Is there a way to do this in GRASS without "growing" my raster
> size or averaging the data prior to analysis?

you can add the needed window sizes to main.c within grass6/raster/r.neighbors

just change line 94, eg: 
	parm.size->options    = "1,3,5,7,9,11,13,15,17,19,21,23,25,100,500" ;

and then compile r.neighbors again as described in the file INSTALL,
section "(G) COMPILING INDIVIDUAL MODULES - OWN MODULES"

-> but larger windows will result in way longer computation times.


Don't know what to do about circular moving windows, though. 
Would like to give it a try myself, but didn't have time to delve into it.


cheers,
  robert