[GRASS-user] New addon: r.denoise. Denoise topography including SRTM

[John A Stevenson]

Hi Frank

Frank Broniewski wrote:
> I want to try your module with my srtm data, but I always get out of memory 
> messages. Maybe I am just to ambitious with my region settings :-) , 
How big a region are you using?  Have you had any luck testing it on a 
smaller region?

I have only ever run out of memory on a 24 million point region, but can 
happily (if slowly) denoise it if I halve the resolution (~6 million 
points).  I have 4Gb RAM.
> but could 
> you provide some hints on general memory usage?
>   
I've emailed Xianfang Sun who wrote the denoising part, (I just wrote 
the GRASS interface) and will let you know what he says.
> Or should I program a script for a moving window so I get smaller regions? Are 
> there any problems then on the connecting borders, e.g. differnently smoothed 
> surfaces at the edges
Each of the cells moves individually based on their neighbouring points, 
so the edges would be smoothed differently.  The magnitude of the 
differences would be very small, but many algorithms e.g. slope, shaded 
relief are very sensitive to them, so I think that they would show up.

Cheers

John

-- 


Dr John Stevenson
Postdoctoral Research Associate
School of Earth, Atmospheric and Environmental Sciences
Williamson Building (Room 2.42)
University of Manchester
Manchester M13 9PL, UK
tel. +44(0)161 306 6585; fax. +44(0)161 306 9361;
john.stevenson at manchester.ac.uk