[GRASS-dev] [r.sun]

[Markus Neteler]

On Thu, Apr 28, 2016 at 1:48 PM, Ben Hur Pintor <bnhr.dev at gmail.com> wrote:
> Thanks for the response. I've seen a lot of literature and uses of r.sun
> which is one of the reasons why I chose it as my model aside from the fact
> that it's open-source. However, most of the uses are European setting which
> I understand since r.sun is based on ESRA. I wanted to see how well r.sun
> performs in a more tropical setting and from my initial findings and
> studies, it seems to be doing pretty well.
>
> r.sun and r.sunmask both seem to use the SOLPOS algorithm, the SPA
> (http://www.nrel.gov/docs/fy08osti/34302.pdf) is a more recent solar
> positioning algorithm by NREL and is much more precise than SOLPOS so I
> wondered if using SPA instead of SOLPOS might provide better results.

Long time back I added the SOLPOS support in r.sunmask.
Do you have a pointer to the SPA source code? Because implementing it
from a 40 pages PDF is expensive :-)

> With regards to using LiDAR-derived raster data, my machine can actually
> handle it but it just takes a lot of time. I have a 1m resolution LiDAR of a
> 500 sq km area (~5GB) and it really just takes a lot of time and disk space
> -- specially for horizon rasters. I'm looking into parallel processing to
> remedy this issue.

You may consider to tile the data (r.tile) with sufficient overlap,
then process these tiles in parallel.

> Lastly, I would also like to go into 3D urban solar energy modelling which
> is why I asked about v.sun or any other attempts in GRASS to develop a model
> for solar radiation received by 3D objects (i.e. buildings including facades
> and roofs).

Yes, here some pointers:

Hofierka and Zlocha, 2012
A New 3-D Solar Radiation Model for 3-D City Models
http://onlinelibrary.wiley.com/doi/10.1111/j.1467-9671.2012.01337.x/abstract

3-D city modeling for sustainable energy applications
http://web.science.upjs.sk/hofierka/projekty/vega2_results.html

Hope this helps for a start,
Markus

-- 
Markus Neteler
http://www.mundialis.de - free data with free software
http://grass.osgeo.org
http://courses.neteler.org/blog