[GRASS-dev] wxGUI GRASS 7: how to drape a map over a DEM?

Markus Neteler neteler at osgeo.org
Sun May 26 01:50:26 PDT 2013

On Sun, May 26, 2013 at 10:32 AM, Anna Petrášová <kratochanna at gmail.com> wrote:
> ok, I get it. You shouldn't load flowacc as a layer because than it is
> displayed as another surface which we don't want in this case. Or when it is
> loaded (when 2D) just uncheck it and adjust the view to see the DEM.

OK - since  I come in the exercise from the 2D view, this may do the trick.
So, in essence, all maps active in the Layer Manager will be treated
as elevation layers in wxNVIZ (?).

> Then,
> go to the Data -> Surface -> Surface attributes and change color to flowacc.
> This should be  the same concept as for the old nviz or not? BTW, it's in
> the video tutorial:)

The old NVIZ I rigorously started from CMD line :-)

nviz elev=elevation colo=flowacc

> The problem why you don't see anything when you load both maps is that
> flowacc has large extreme values, so the initial view is confused.

Indeed, I am surprised (extra unrelated issue) that flowacc has this

r.univar flowacc
total null and non-null cells: 525000
total null cells: 0

Of the non-null cells:
n: 525000
minimum: -253898
maximum: 15278.2
range: 269176
mean: -275.776
mean of absolute values: 311.452
standard deviation: 4199.2
variance: 1.76333e+07
variation coefficient: -1522.69 %
sum: -144782397.558392

> Anyway
> you should be able see something when you adjust the view to some normal
> height.

Thanks, Anna. I'll get to speed with it for sure.


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