[GRASS-user] r.drain problem when flow reach the border

[Milton Cezar Ribeiro]

Hi Markus

You are right. Thanks for your comments. In fact I don´t thougth on
null cell between Source and Target, and agree that extent influences
one archive or not a real least cost path solution.

Cheers

miltinho

2012/12/27, Markus Metz <markus.metz.giswork at gmail.com>:
> On Wed, Dec 26, 2012 at 10:01 PM, Milton Cezar Ribeiro
> <miltinho.astronauta at gmail.com> wrote:
>> Hi Mohamed and Markus
>>
>> Mohamed, thanks for your reply, I will wait for a solution within GRASS
>> :-)
>>
>> Markus, thanks for your reply,. Sorry  but I disagree a tiny bit,
>> because is expected that between a source and target I will find a
>> solution with the Least Cost path. Do you think that is there any
>> situation where a least cost between source and target will not be
>> found? Maybe if other software provide the soluction, although is not
>> the bestest option, I prefere receive one complete output than a
>> broken one.
>
> Ah, you are right, if the input is output from r.cost, the cost
> directions should be used. Depending on the input data and the region
> extents, the least cost path found may not be the real least cost
> path, but there should be one solution.
>
> There are situations where there is no connection between source and
> target if source and target are separated by NULL cells and no NULL
> cost is specified to r.cost.
>
> Markus M
>>
>> Happy new year!
>>
>> miltinho
>>
>> 2012/12/23, Markus Metz <markus.metz.giswork at gmail.com>:
>>> On Sun, Dec 23, 2012 at 7:07 PM, Milton Cezar Ribeiro
>>> <miltinho.astronauta at gmail.com> wrote:
>>>> Dear all,
>>>>
>>>> I am running a least cost path analysis combining r.cost and r.drain.
>>>> But on some cases, when the least cost path between source and target
>>>> reach the border of my map, r.drain stop on that position, and target
>>>> point isn´t reached.
>>>
>>> This is correct because at the borders, the direction can not be
>>> determined, the path could lead out of the current region, you can not
>>> tell.
>>>
>>> Running on other softwares the algorithms the
>>>> source and target is connected using edges without problem.
>>>
>>> If in doubt, I would call it a bug in that other software.
>>>
>>>>
>>>> Any hint are welcome.
>>>
>>> Try to expand the current region
>>>
>>> Markus M
>>>
>>
>>
>> --
>> Miltinho - mcr at rc.unesp.br
>> Laboratório de Ecologia Espacial e Conservação - LEEC
>> Depto de Ecologia - UNESP - Rio Claro
>> Av. 24A, 1515- Bela Vista
>> 13506-900 Rio Claro, SP, Brasil
>>
>> Fone: +55 19 3526-9647 (office)  19 3526-9680 (lab)
>> Cel: 19 9853-3220 / 19 9853-5430
>>
>> Depto Ecologia http://www.rc.unesp.br/ib/ecologia/
>>
>> PG ECO & BIODIV
>> http://www.rc.unesp.br/ib/ecologia/posbiodiversidade/index.php
>>
>> CV
>> http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4792988H6&mostrarNroCitacoesISI=true&mostrarNroCitacoesScopus=true
>>
>> Google citations http://scholar.google.com/citations?user=OWX_2eAAAAAJ
>


-- 
Miltinho - mcr at rc.unesp.br
Laboratório de Ecologia Espacial e Conservação - LEEC
Depto de Ecologia - UNESP - Rio Claro
Av. 24A, 1515- Bela Vista
13506-900 Rio Claro, SP, Brasil

Fone: +55 19 3526-9647 (office)  19 3526-9680 (lab)
Cel: 19 9853-3220 / 19 9853-5430

Depto Ecologia http://www.rc.unesp.br/ib/ecologia/

PG ECO & BIODIV http://www.rc.unesp.br/ib/ecologia/posbiodiversidade/index.php

CV http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4792988H6&mostrarNroCitacoesISI=true&mostrarNroCitacoesScopus=true

Google citations http://scholar.google.com/citations?user=OWX_2eAAAAAJ