[GRASS-user] r. walk and sites which can be reached in a certain time

[Markus Metz]

On Mon, Oct 24, 2016 at 4:34 PM, Anna Petrášová <kratochanna at gmail.com> wrote:
> On Mon, Oct 24, 2016 at 10:22 AM, Phil Burgdorf <P_Burgdorf at web.de> wrote:
>> Hi Anna,
>> thanks for your answer. I've tried to use 3600 as max. Cost but the
>> algorithm failed.
>
> That's weird.
>
>> The values for min and max for the cummulative cost are "nan". But I don't
>> know why!

This is most probably a problem of the computational region not set to
the input elevation. Also, the grid geometry (extents and resolution)
of the friction raster must match the elevation raster.

Compare g.region -p with r.info of the input elevation and input friction.

Markus M


>> How can I do this in r. mapcalc. I haven't used it before
>
>
> r.mapcalc "time_to_walk_limited = if(time_to_walk < 3600, time_to_walk, null())"
>
> Please keep the discussion on the mailing list.
>
>
>> Phil
>>
>> Gesendet: Montag, 24. Oktober 2016 um 16:02 Uhr
>> Von: "Anna Petrášová" <kratochanna at gmail.com>
>> An: "Phil Burgdorf" <P_Burgdorf at web.de>
>> Cc: "GRASS user list" <grass-user at lists.osgeo.org>
>> Betreff: Re: [GRASS-user] r. walk and sites which can be reached in a
>> certain time
>> On Mon, Oct 24, 2016 at 7:52 AM, Phil Burgdorf <P_Burgdorf at web.de> wrote:
>>> Hello there,
>>> my name is Phil and I'm a PhD Student in Archaeology and I'm analiesing a
>>> small area in bavaria. I'm trying to locate archaeological sites round
>>> different strating points. Therefor I created a cost map using r. walk.
>>> The
>>> result is fine but how can I adapted my values. Actualy I'm interrested in
>>> sites which can be reached in, let's say, one hour. I've tried to change
>>> the values for max costs but I didn't get any results. Do i have to use a
>>> nother algorithm? here must be an easy way to define the max cost for that
>>> analysis.
>>>
>>> I couldn''t find any help in the mailing list's archive and I#m totally
>>> lost. Can you help me?
>>
>> max_cost will do the trick, don't forget that the time is in seconds.
>> You can also use raster algebra (r.mapcalc) to extract the area within
>> certain time.
>>
>> Anna
>>
>>>
>>> Cheers
>>> Phil
>>>
>>>
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>>> http://lists.osgeo.org/mailman/listinfo/grass-user
>>
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