[GRASS-user] Understanding Raster Map Input Files

Wed Sep 5 10:47:58 PDT 2018

Hi Pedro,

Thank you for the reply and it helped me a lot. So here what I did. I
needed to create the raster file such wind speed is 230 ft/min. So I used
the following command.

r.mapcalc "new_wind_speed = 350"

Then I run the fire behavior module and observed the changing of the
spread. Did the same procedure for wind direction.

r.mapcalc "new_wind_direction = 50"

I want to know that whether what I did was correct and is it the right way
to create input raster file.

BR,
Vidura Dantanarayana.

On Mon, Sep 3, 2018 at 4:52 PM Pedro Venâncio <pedrongvenancio at gmail.com>
wrote:

> Hi Vidura,
>
> Just like Moritz said, you need to start by the basics about GRASS.
>
> That said, it is better to create new raster layers than change the
> existing ones.
>
> To test other wind speed and direction, moisture, etc, just create new
> rasters with r.mapcalc
>
> https://grass.osgeo.org/grass74/manuals/r.mapcalc.html
>
> Start with constant rasters, using the example in the r.mapcalc manual.
>
> Best regards,
> Pedro Venâncio
>
>
> A seg, 3/09/2018, 06:22, Vidura Dantanarayana <vidurada at gmail.com>
> escreveu:
>
>> 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
>>>>>
>>>> _______________________________________________
>>>> grass-user mailing list
>>>> grass-user at lists.osgeo.org
>>>> https://lists.osgeo.org/mailman/listinfo/grass-user
>>>
>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-user/attachments/20180905/01031fa2/attachment.html>