[GRASS-user] r.sun problem

[Dylan Beaudette]

All this recent talk about bugs in r.sun / r.sun2 has made me a bit
concerned about recent research built on r.sun. Should I be concerned
about incorrect results from r.sun when supplied with an aspect +
slope map, as run on GRASS 6.4, about 2 years ago?

Thanks,

Dylan

On Sat, Aug 22, 2009 at 6:56 AM, Hamish<hamish_b at yahoo.com> wrote:
> Hi,
>
>> I am using r.sun -s to calculate solarmaps for each month.
>> I wrote a shell script which calculates every 10th day
>> (including the shaddowing effect). But something is going
>> wrong. I looks like the shaddows are displaced somehow (see
>> attachement). Using r.sun2 -s didnt make any difference.
>> Curiously once it worked! But although I'm using the same
>> projection, location, mapset and DSM - it doesnt work
>> anymore.
>>
>> I hope anybody could help me out or have any ideas how I
>> could solve this problem....I really need these maps.
> .....
>> I am using Quantum Gis Version 1.0.2 and GRASS 6.4.0 svn
>>
>>
>> The region  of my investigation area is:
>>
>> $ g.region -p
>> projection: 99 (Transverse Mercator)
>> zone:       0
>> datum:
>> towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232
>> ellipsoid:  bessel
>> north:      281981.20714553
>> south:      281612.20714553
>> west:       -29172.52857137
>> east:       -28383.52857137
>> nsres:      1
>> ewres:      1
>> rows:       369
>> cols:       789
>> cells:      291141
>
>
> could you provide the exact command line you were using?
> are you using r.horizon seeds, or slope and aspect seed maps?
> what time step?
>
> By chance I noticed in xpdf if I dragged with the left mouse
> button instead of the middle one (to pan) I got an inverse
> image which made the effect a bit clearer. With that I notice
> that the center-southmost  building in the "ok" map actually
> isn't.
>
> how do you run the two different versions? did you compile the
> old one? is this the latest SVN? (like younger than a week?)
> is QGIS only used for visualization or do you run grass from
> the toolbox?
>
> lately we have been running some tests with it*, but in general
> I think the new version (ie really upgrade) is in fact better
> than the old, if just because you can avoid the slope/aspect
> bug now.
>
> [*] see http://grass.osgeo.org/wiki/r.sun
> and https://trac.osgeo.org/grass/ticket/498
>
>
>
> building shadows is something I'd always wanted to try with
> r.sun, interesting to see some results! May I ask if it is
> LIDAR elevations or simply by e.g. number of storeys?
>
> also, may I suggest "r.colors map color=grey -e", where the -e
> flag may help mute the contrasts a bit.
>
>
> Hamish
>
>
>
>
>
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