[GRASS-user] r.horizon and negative tilt

[Frank David]

Ho yes, why not. I  could use r.viewshed to find the farest part of the
topography able to see my point and get it's angle mode. The trick to
find is how to get that cell ?
Best regards,
frank

Le 30/07/2018 à 11:18, balotti.and at gmail.com a écrit :
> Il 30/07/2018 09:24, Frank David ha scritto:
>> Hi Andrea,
>> Thanks for your message. But what is the ground plane ? r.horizon use
>> the topography, so nothing is plane (and the earth curvature tends to
>> lower the ground). 
> Yes, what you explain below is what I mean with "ground plane".
>> I guess as the calculation is done at ground level, the minimum
>> viewable horizon cannot be lower than zero. The calculation should be
>> done higher than ground level to "see" negatives horizon.
> Have you taken a look to r.viewshed? I never tried it but maybe is
> useful for your purposes.
>> Never mind I will try to create my own r.horizon with r.transect or
>> r.profile.
>> Best regards,
>> Frank
> Best regards,
> Andrea
>
>> Le 30/07/2018 à 08:47, balotti.and at gmail.com a écrit :
>>> Hi Frank,
>>> just my opinion but r.horizon I suppose is targeted to solar
>>> radiation modules and because of that returns only the line-of-sight
>>> "obstacles" above the ground plane, where direct sunlight may be
>>> obstructed by obstacles.
>>> best regards,
>>>
>>> Andrea Balotti
>>>
>>> Il 28/07/2018 15:59, Frank David ha scritto:
>>>> Dear all,
>>>>
>>>> It seems that r.horizon in does not return negative heights. How
>>>> it's possible in case of the given point from the calculation is
>>>> done is located on mountain and the horizon around is below zero
>>>> ??. I miss something may be...
>>>>
>>>> Thank you for your explanations
>>>>
>>>> Regards
>>>>
>>>> Frank 
>
>
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