[GRASS-user] Understanding Raster Map Input Files

Sun Sep 2 22:22:20 PDT 2018

Hi Pedro,

Thank you very much for the explanation. That helped me to get a basic idea
of what these files do. Then what I did was to change these files. I
changed some records in wind speed and wind direction (the files in
demomapset/cats). But what I observed was there was no change in the shape
of spread even after the alterations. Is there anyone who willing to help
me in crating custom files if I provide the relevent information. I need to
crate wind, moisture, and fire origin files.

BR,
Vidura Dantanarayana.

On Sat, Sep 1, 2018 at 7:23 PM Pedro Venâncio <pedrongvenancio at gmail.com>
wrote:

> Hi Vidura,
>
> You need to prepare the input data to r.ros algorithm
>
> https://grass.osgeo.org/grass74/manuals/r.ros.html
>
> The input data needs to be in raster format.
>
> First you need to use the standard NFFL 13 fuel models system (
> https://www.fs.fed.us/rm/pubs/rmrs_gtr153.pdf) as fuel model input raster.
>
> You also need the fuel moisture content for all sizes and response times
> (dead 1h, 10h, 100h and live), in percentage.
>
> As Moritz explained to you, you can see that the 1hour_moisture raster of
> the sample data is composed by:
>
> - 3% moisture in areas of fuel model 4;
> - 15% moisture in areas of fuel model 8.
>
> You can give homogeneous fuel moisture content for each response times, or
> different if you have that information, like in the sample data.
>
> Then you need an elevation raster (DEM), calculate slope and aspect (if
> you don't have them yet, with r.slope.aspect), and a raster with wind speed
> (in feet/minute) and another with wind direction (clockwise from north, in
> degrees).
>
> With this data, you run r.ros and with the output rasters, run r.spread
>
> https://grass.osgeo.org/grass74/manuals/r.spread.html
>
> r.spread just need the an additional raster, with the ignition(s)/starting
> sources. Pixels of starting sources raster needs to be only values of 1
> (ignition points/areas) and 0 (other areas). If you have the ignitions in
> vector format, just use v.to.rast.
>
> I hope this helps.
>
> Best regards,
> Pedro Venâncio
>
>
>
> Vidura Dantanarayana <vidurada at gmail.com> escreveu no dia sábado,
> 1/09/2018 à(s) 14:12:
>
>> Hi all,
>>
>> Thank you very much Moritz Lennert for the explanation and apologize for
>> the mistake I've done. I will try what you suggest by myself.  Hope It's
>> okay to questioning again if I found a problem again. Have a wonderful day.
>> Cheers!!!
>>
>> BR,
>> Vidura Dantanarayana.
>>
>> On Sat, Sep 1, 2018 at 2:04 AM Moritz Lennert <
>> mlennert at club.worldonline.be> wrote:
>>
>>> Hi Vidura,
>>>
>>> First of all, please keep discussions on the list.
>>>
>>> On 31/08/18 09:48, Vidura Dantanarayana wrote:
>>> > Hi Moritz,
>>> >
>>> > Really appreciate your help as we are facing this problem for some
>>> days
>>> > now. First I'm a beginner user. Can you explain what are the
>>> categories
>>> > and how those used in GRASS GIS?
>>>
>>> GRASS GIS is an extremely wonderful and powerful tool, but it does need
>>> some initial learning in order to understand how to use it. Just
>>> answering the questions below will not provide that for you.
>>>
>>> I would suggest that you go through some of the basic introductory
>>> material, just in order to get a feeling for GRASS GIS, before attacking
>>> your specific problem.
>>>
>>> You could have a look at the following resources (at least for their
>>> introductory parts):
>>>
>>> - https://grass.osgeo.org/grass74/manuals/helptext.html
>>> - https://grass.osgeo.org/grass74/manuals/rasterintro.html
>>> - https://grass.osgeo.org/grass74/manuals/vectorintro.html
>>> -
>>>
>>> https://grasswiki.osgeo.org/wiki/From_GRASS_GIS_novice_to_power_user_(workshop_at_FOSS4G_Boston_2017)
>>> -
>>>
>>> http://www.training.gismentors.eu/isprs-summer-school-2016/lesson1/grass-gis.html
>>>
>>> Or search for "GRASS GIS" in YouTube for some videos.
>>>
>>> > Let's say I need to create custom
>>> > 1hour_moisture (or any other file), so how can I create these files?
>>>
>>> How you create these files depends on the data that you have as input.
>>>
>>> If you look at the metadata of the file in the demolocation
>>> (right-click->Metadata or 'r.info 1hour_moisture' you will this
>>> information at the end:
>>>
>>> |   Data Description:
>>>      |
>>> |    generated by r.mapcalc
>>>      |
>>> |
>>>      |
>>> |   Comments:
>>>      |
>>> |    if(fuel_class==4,3,if(fuel_class==8,15))
>>>
>>>
>>> This means that the authors had a raster file called 'fuel_class' and
>>> used the raster calculator (r.mapcalc) to reclass that file attributing
>>> the value 3 to those pixels who had class=4 in the original map and
>>> value 15 to pixels with class=8.
>>>
>>> I have no idea what this original map contained, so cannot help you
>>> further (I don't know much about fire spread modeling).
>>>
>>> > Can
>>> > you look at the following problem again?
>>> >
>>> >
>>> > # 1 categories ----------------------------------------------------->
>>> (1)
>>> > Map of Fire Origin of Bass River Fire --------------------> (2)
>>> >
>>> > 0.00 0.00 0.00 0.00 ---------------------------------------------> (3)
>>> > 0:no data ----------------------------------------------------------->
>>> (4)
>>> > 1:fire origin
>>> ---------------------------------------------------------> (5)
>>> >
>>> > I need to know how to customize the location of origin. I mean, I want
>>> > to ignite the fire from another place rather the place specified in
>>> demo
>>> > data.
>>>
>>> If you have the origin location as coordinates, you can create a vector
>>> point at the location using v.in.ascii: in the GUI of that module you
>>> can enter coordinates interactively. Then you convert the map to a
>>> raster map using v.to.rast.
>>>
>>> Moritz
>>>
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