[GRASS-user] Downscaling and aggregating raster categories/classes

[Nikos Alexandris]

For whom it may be of interest!

Nikos Alexandris wrote:
> I am trying to perform the following:
> 
> A classified map  "A"  of 25m pix res. has two main categories B and C.
> Downscaling the map to 50m (map  "B") results in pixels which correspond to
> 4 * 25m (original pixels).
> 
> Given the region extent is aligned, three possibilities may occur (near the
> borders between categories B=11 and C=22) in terms of abundance/coverage in
> the resampled map:
> 
> 1. B = C  <-- Mixed (M)
> ____
> 
> |B|B|
> |-----|
> |C|C|
> 
> -------
> 
> 2. B > C
> 
> |B|B|
> |-----|
> |C|B|
> 
> -------
> 
> 3. B < C
> 
> |B|C|
> |-----|
> |C|C|
> 
> -------

..

I did:

#1
r.resamp.stats input=A output=B method=sum # map A has two cats: 11 & 12

#2
r.mapcalc "B_int = int( B )"

# 3
r.recode in=B_int out=B_int_recoded rules=RecodingRules

where RecodingRules contains:

44:44:11:11
45:45:11:11
46:46:13:13
47:47:12:12
48:48:12:12 

where class B = 11, class C = 12 and a (new) Mixed class is M=13.

It would be nice to get this in one step :-)

Best, Nikos
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