[GRASS-user] Re: i.sunhours
hamish_b at yahoo.com
Tue Jan 26 21:45:53 EST 2010
Tim Michelsen schrieb:
> > > what do the inputs for i.sunshine in GRASS7 mean?
> > >
> > > i.sunhours doy=name lat=name
> > I guess
> > doy = day of year
> > lat = latitude
> > While doy in (1-365)
> > And lat in (0-90)?
> > Should be. But why "name"??
> I thought the same.
> But the doc is strange:
> Name of the doy input map
DOY is day of year, and it is a raster map, but I'm not sure if
it should be 0-365, 1-366, 1-365, 0-365.25, ...
a lot of the other GIPE modules (grass-addons) use that, but I have
no idea why it wants those to be in raster maps instead of just a
single integer day or floating point day+hours/24+minutes/1440.
maybe it is intended for satellite passes where there could be a
different time-of-day as the sat passes overhead or for multiple
passes on the same image? ?? no idea.
also from our tests with r.sun I'm not sure how much time a pre-formed
lat= map really saves vs. calculating it e.g. once per raster row with
the proj library, or even calculating for each individual cell on-the-
fly. see https://trac.osgeo.org/grass/ticket/498, the r.sun page in the
wiki, and the threads on the -dev mailing list about it.
the documentation does need a lot of enhancement.. perhaps there is more
documentation in the GIPE section of the addons SVN? there are some
examples there anyway.
it seems the modules still need a bit of GRASSification done to them too.
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