[GRASS-user] No Data everywhere when I extract the shadow from a DEM using r.sunmask

[Hakim Benoudjit]

Thanks guys for the quick response.
You were right, the shadow wasn't detected because the region hasn't been
set.

Now it seems to be working, but I'm wondering between `r.sunmask` and
`r.sun` which one should be used to calculate the shadow mask?

Thanks.

Hakim.


On 4 September 2017 at 15:43, Micha Silver <tsvibar at gmail.com> wrote:

>
>
> On 09/04/2017 05:15 PM, Hakim Benoudjit wrote:
>
> Hello,
>
> First of all, I'm new to this mailinglist and to GrassGIS in general.
>
> Welcome
>
>
> So, I'm trying to use the `r.sunmask` command in order to extract the
> shadow from an `SRTM DEM` of the Alps mountains (Switzerland).
> The image had to be first `reprojected` when I've imported it to a
> `EPSG:21781` location, in order to get both the (lat, lon) in meters
> (similarly to the elevation).
>
> Here is the command I'm executing (note that the time of the day was
> chosen at 09:00 in the morning to maximize the shadow):
>
> r.sunmask elevation=n46_e006_1arc_v3 at PERMANENT output=alps-sunmask.tif year=2014 month=9 day=23 hour=9 minute=0 timezone=1
>
>
> The problem I have is that the image produced is emtpy (no-data
> everywhere).
> Is there a parameter I'm forgetting to add to the `r.sunmask` command?
> Or should I use `r.sun` command instead, even though I'm not sure about
> the parameters I should provide to it either ?
>
> Most likely you need to set the region to your DEM.
> g.region -p rast=n46_e006_1arc_v3 at PERMANENT
>
> FAQ #1 when using GRASS: Always set the region first
>
>
> Hakim.
>
>
> _______________________________________________
> grass-user mailing listgrass-user at lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/grass-user
>
>
> --
> Micha Silver
> Ben Gurion Univ.
> Sde Boker, Remote Sensing Lab
> cell: +972-523-665918
>
>
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