[GRASS5] v.surf.idw new parameter power

Wolf Bergenheim wolf+grass at bergenheim.net
Wed Dec 7 03:19:06 EST 2005


On 06/12/05 16:31, Hamish wrote:
>>I needed to be able to modify the power of the distance part of the
>>idw algorithm (the beta). Well I did it, and I've attached the diff.
> 
> 
> often refered to as the "coefficient of friction", 1/d^Cf 
> 
> A value of 2 gives the smoothest result, but values greater than two
> will help to constrain open boundary effects. A compromise is to run at
> 2.5 or run the module twice, once for Cf=2 and once for Cf=3. Then use
> r.series or r.mapcalc to average the results. Values at real data points
> should be the same, only the interpolated values are tweaked, so legal.

Thanks. That was new to me (well almost everything in GIS is new to me).

> 
> For giggles, other radial basis functions can be inserted too. (log() etc)
LOL. That could be fun. Perhaps I could add another parameter
'radial_basis', or something, which could take arguments like 'log'
'power' and then add the parameter 'base' that would be used as the base
of the log operation.

--Wolf

> Hamish
> (I have an interesting paper to publish on this at some point)
> 

I'm looking forward to reading it (:

-- 

<:3 )---- Wolf Bergenheim ----( 8:>




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