[GRASS-user] v.vol.rst basic questions

[Hamish]

Christian Ferreira wrote:
> Actually, here I have a very strange thing... 
> 
> If I run g.list rast3d, I can list my interpoled volume.
> 
> But if I try to run "r3.info ctd_volume2" in the
> command line I get a message 
> 
> telling "ERROR: Raster map <ctd_volume2> not
> found", but if I use the GUI for
> r3.info is possible to read the
> file (like above). 
>
> The same happens if I try start nviz with:
> 
> "nviz bathy volume=ctd_volume2"

no idea.


> Aham. So, this means that v.vol.rst is not supposed to be used with
> Lat-Long?

no idea, I'm just speculating based on the fact that lat/lon adds a lot
of complication and the coder would have to had specifically written
in special support for it.


> If yes, I will definitely quit this Lat-Long location and
> go to UTM.

try both, see which way works best....


> Well, after trying the whole Friday with nearlly no
> results, I'm quite convinced that v.vol.rst is not dumb.

I meant that in the sense of it may not be lat/lon aware, not at all
that it was a stupid program.

> Here is a try adjusting res3 to 0.000278 (30m), zmult to
> the same number and dmin to 0.001
> 
> http://picasaweb.google.com/chris.for.lists/Map#5334573425418213906

volume seems 90deg roated?!

Hamish:
>> actually the thing that I worry about there is not the x,y with z
>> using different units (easily fixed by reprojecting to a
>> planimetric projection), it is that all of your data points are
>> essentially in a single straight line, and what effect that has on
>> the 3D algorithm?
Christian:
> As long I'm capable to produce a 2D slice along the transect/volume 
> to show the data, the rest would not matter for the moment.
> 
> But I understand that interpolation algorithm is having a
> hard time when trying to interpolate the cells away from
> the transect.

again, I'm no expert at all with the module, just guessing.
certainly all interpolation modules will have problems extrapolating
through unconstrained boundaries to some extent.


> This was a test... the best is probably how you are saying
> below... 

it is a good test to do..
have you done the same thing with UTM before had had good results?

> Well, is not better (or possible) to set in GRASS a
> temporary region so thin (in the N-S axis) to create this 2D slice?

sure, but I meant it was a 2D problem (x vs z) and you could fool the
GIS into using its 2D x,y tools to solve the x,z problem then rotate
the cells back to the correct orientation.


>> and also maybe some r3.out.vtk stuff with Paraview or Vis5D?
> 
> I'm trying to simply do all using GRASS... maybe is not
> the best choice.

as good as any, better than most. :)
just different tools for the job to explore.


Hamish