[GRASS-user] Resampling with percent cover

[Hamish]

> Ned Horning wrote:
> > Hi � I am still working on creating a percent shrub cover map using
> > GRASS and R and have a question regarding resampling. I have
> > shrub/non-shrub/cloud maps at 1m resolution and I want to resample
> > those to 30m pixels using the following logic.
> > 
> > The value of each output 30m pixel will be the percentage of shrub
> > pixels that make up the corresponding 30 x 30 pixel area from
> > the shrub/non-shrub/cloud map and if any of the pixels in the 30 x 30
> > pixel area has a cloud value the value of the resulting 30m pixel will
> > be NULL.
> >
> > Is there a way to do this in GRASS? R.resamp.stats seems like it is
> > close but that might be too difficult for me to modify.

Glynn wrote:
> There shouldn't be any need to modify it.
> 
> Create a reclass of the input such that shrub=1, non-shrub=0 and
> cloud=null, then resample that with "r.stats -n method=average ...".

(... that should read 'r.resamp.stats' not 'r.stats')
 
> The value of each output cell will be the proportion of shrub cells in
> the corresponding 30x30 block of input cells, in the range 0.0 to 1.0
> (if you want 0-100, use r.rescale or r.mapcalc). With the -n flag, if
> one or more of the input cells in a 30x30 block are null, the
> corresponding output cell will be null.