[GRASS-user] percentage of class in raster within polygons

[Paulo van Breugel]

I haven't tested it, but the fastest way could be to rasterize your polygon
layer (using the resolution of the input raster or higher resolution - make
sure to assign an unique id to each grid cell before) and then use r.stats

r.stats -a -p input=rasterized_polygon,raster

Rgds,

Paulo


On Wed, Feb 11, 2015 at 12:15 PM, Margherita Di Leo <diregola at gmail.com>
wrote:

> Hi,
>
> I have to calculate the percentage of given class of a raster within the
> polygons given in a vector (a regular grid). Since I'm dealing with large
> files and operations repeated in a chain, i should be focusing on what is
> the optimal (fastest) option to do that. I could vectorize the raster and
> use v.overlay and v.to.db, or using v.rast.stats i can count out the number
> of cells (should i use number for that or sum?) and then divide per  area
> of the grid. Any better idea?
>
> Thank you in advance
>
> --
> Best regards,
>
> Dr. Margherita DI LEO
> Scientific / technical project officer
>
> European Commission - DG JRC
> Institute for Environment and Sustainability (IES)
> Via Fermi, 2749
> I-21027 Ispra (VA) - Italy - TP 261
>
> Tel. +39 0332 78 3600
> margherita.di-leo at jrc.ec.europa.eu
>
> Disclaimer: The views expressed are purely those of the writer and may not
> in any circumstance be regarded as stating an official position of the
> European Commission.
>
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