[GRASSLIST:4516] Re: filter out extrem values

[Gordon Keith]

On Mon, 16 Sep 2002 21:45, Malte Martin wrote:
> Hi!
>
> I got 35000 points where I measured the depths of a lake. Now I have
> to filter out the extrem values (maybe by moving average?).
>
> I want to interpolate the surface of the lake bottom.

Could you please let me know what you come up with.

I'm also working with lots of points of bathymetry data (swath mapper) 
and haven't found any particularly good solutions yet in grass. (my 
biggest sites files has 31,252,537 points).

If it's of any use I have a modified version of s.to.rast which has 
methods of handling multiple points in a cell. The method options are: 
single, first, last, minimum, maximum, count, sum.

Minimum and maximum may be of use in quality checking, but I can't see 
how to use them for data cleaning.

I'd love to have a median option in s.to.rast but haven't got around to 
anything like that yet (a lot more work that the above methods). A 
combination of s.windavg and s.univar would be nice. I haven't looked 
at the code for either yet, I doubt they are easy to combine.

Regards
Gordon

-- 

Gordon Keith
Programmer/Data Analyst
Marine Acoustics
CSIRO Marine Research
http://www.marine.csiro.au

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