[GRASS-user] Understanding Raster Map Input Files

Mon Sep 3 04:21:57 PDT 2018

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
>>>>
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>>
>>
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