[GRASS-user] r.horizon and negative tilt

[balotti.and at gmail.com]

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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