[GRASS-user] resampling and patching DEM

[Silvia Simoni]

Thanks Glynn,

one more comment below...

On Nov 5, 2008, at 11:15 PM, Glynn Clements wrote:

>
> Silvia Simoni wrote:
>
>> I need to patch dems with different resolutions (1x1m) and (2x2 m)  
>> and
>> resample them to a coarser resolution (10x10 m). Which is the correct
>> procedure?
>>
>> a. resampling the 1x1 dem to 2x2 using r.resampl.stats -w (to be more
>> accurate)
>> patch them all at 2x2, resample the patched dem to 10x10m;
>>
>> b.resample the 1x1 and 2x2 dem to 10x10 m separately using
>> r.resampl.stats -w, and then patch them all.
>
> In most cases, the most accurate approach is to set the region to 1x1,
> patch (which will resample everything to 1x1 by nearest-neighbour),
> then resample to 10x10 with r.resamp.stats.
>
> The problem with patching down-sampled data is that r.patch won't
> merge partial results at the boundaries. It will simply discard choose
> one value and discard the others.

Then why don't patch all 1x1 tiles together, resample them to 10x10  
with r.resamp.stats, doing the same for the 2x2 tiles (patching and  
resample), and finally patching the two obtained maps?

silvia

>
>
> -- 
> Glynn Clements <glynn at gclements.plus.com>

----------------------------------------------------------------------------------------
Silvia Simoni PhD
DICA - Department of Civil and Environmental Engineering
Universita' di Trento
via Mesiano 77, 38100 Trento, ITALY
tel. +39 0461 882610
fax. +39 0461 882672
e-mail: silvia.simoni at ing.unitn.it