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

Nikos Alexandris nik at nikosalexandris.net
Mon Oct 15 08:01:49 PDT 2018

Please post the exact command you have used (copy-and-paste).

Then, what does
r.category spread_time_observed

and what does
r.report spread_time_observed units=c,p


* Kalindu Perera <kkc199408 at gmail.com> [2018-10-15 16:01:38 +0530]:

>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

Nikos Alexandris | Remote Sensing & Geomatics
GPG Key Fingerprint 6F9D4506F3CA28380974D31A9053534B693C4FB3 
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