[Qgis-user] Processing Saga Raster Volume

[Lene Fischer]

Hi Nyall,
Thanks for the new Raster surface volume in processing. My students will love it!
They just finalized their GIS exam manually calculating raster volume for a lake with different sea levels. This functionality would have saved them hours.

Just have to get used to a negative volume when calculating below sea level. :-)

Kind regards
Lene Fischer


-----Oprindelig meddelelse-----
Fra: Nyall Dawson [mailto:nyall.dawson at gmail.com] 
Sendt: 20. januar 2019 06:52
Til: Lene Fischer
Cc: qgis-user at lists.osgeo.org
Emne: Re: [Qgis-user] Processing Saga Raster Volume

On Sat, 19 Jan 2019 at 18:53, Lene Fischer <lfi at ign.ku.dk> wrote:
>
> Hi,
>
> I´m trying to calculate a raster volume using Saga Raster Volume.
>
> The process run smoothly in 5 sec., but I can´t see the result.
>
> I have the processing log  and result viewer open - but I get no result.
>
>
> I have a work around with the Raster calculator and zonal statistic - but I prefer the Saga version.
>
> Is it a bug or ?

Debatable. The volume IS there, it's just hidden in the middle of all
the SAGA terminal output in the log view. You can't automatically save
the volume, or use it within a Processing Model. So - it works, but
the SAGA tool has limited value. Personally, I'd say yes, a bug.

But the good news is that the algorithm is trivial to port to QGIS,
which I've done in https://github.com/qgis/QGIS/pull/8912. With any
luck we can get this new native tool included in 3.6, so we'll have a
good out-of-the-box algorithm available which calculates the volume,
allows saving it to a HTML report or vector table, and allows use of
the calculated volume within a Processing model.

From the PR description: "...honestly, if Lene struggles with a QGIS
tool, that indicates that the tool has issues -- not the user..." ;)

Nyall

>
>
>
> Regards
>
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> Lene Fischer
>
> Associate Professor
>
>
>
> University of Copenhagen
>
> Department of Geoscience and Natural Resource Management
>
> Forest and Landscape College
>
> Nødebovej 77a
>
> 3480 Fredensborg
>
> Denmark
>
>
>
>
>
> MOB +45 40115084
>
> lfi at ign.ku.dk
>
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