[GRASS-user] How to get the area of a polygon in a layer

Kalindu Perera kkc199408 at gmail.com
Mon Oct 15 03:31:38 PDT 2018

Dear Nikos,

We have used r.ros and r.spread commands for getting the wildfire
After that, the output from the r.spread command is spread_time_observed
layer(This is the output from the simulation)
We use that layer as the input layer for the r.surf.area command.

We got many area outputs from that command output and couldn't identify
what area gives the area of the "burned" area
* I have attached the output from running r.surf.area command as an

** Another question how we can extract only the "burned" area from the
spread_time_observed layer?

Thanks a lot for the quick reply
Looking forward to more knowledge

Best Regards
Kalindu Perera

On Mon, 15 Oct 2018 at 15:07, Nikos Alexandris <nik at nikosalexandris.net>

> * Kalindu Perera <kkc199408 at gmail.com> [2018-10-15 13:28:15 +0530]:
> >Dear all,
> >
> >We are doing wildfire simulation in Grass GIS. We need to compare the area
> >of 2 wildfire spreads after wildfire simulation ran. We tried to calculate
> >the area of the spread using r.surf.area module. But we couldn't identify
> >which is the area of the simulation from areas given from that. Could
> >anyone tell us how to get an area from spread like this?
> Dear Kalindu,
> please post exact commands you already tried.
> What are the simulation output maps?
> Fitst, what does `r.category` and `r.report` return when used for
> simulation
> maps?
> Then, maybe you need to "extract", each time, the "burned" area, then
> use `r.surf.area` on it?
> Nikos
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